At least 13 US service members killed in Kabul airport attack

An additional US service member has died as a result of the attack at the Kabul airport Thursday, according to a statement from US Central Command.

A total of 13 US service members were killed Thursday and the total number injured is now 18, said Capt. Bill Urban, a spokesperson for CENTCOM.

Urban said the injured are in the process of being evacuated from Afghanistan.

"Our thoughts and prayers continue to be with the injured and to the friends and family of those who were killed," he added.

The White House responded to Republicans calling on President Biden to resign in the wake of recent bombings in Kabul, telling reporters “it’s not a day for politics.”

Three Southern California families who became stranded in Afghanistan while visiting relatives over the summer have made it safely out of while five others remain stuck as chaos continues to unfold around the nation’s main airport.

Two families departed Afghanistan Thursday, according to Howard Shen, spokesperson for the Cajon Valley Union School District, near San Diego. A third family had also departed and returned to the US on Wednesday, he said. 

Shen estimated that five additional families from the school district, consisting of 14 students and eight parents, are still in Afghanistan. The figure marked an increase from Wednesday when Shen believed that a total of six CVUSD families were in Afghanistan, noting that information is fluid and constantly evolving. He said the district is working with California Rep. Darrell Issa’s office, and other national security officials to assist the families with a safe exit. 

The departures come as deadly explosions rocked the area outside Kabul’s airport on Thursday as the US and other Western countries raced to complete a massive evacuation of their citizens and Afghan allies following the Taliban takeover of the country. 

President Biden on Thursday vowed to continue evacuations despite the terror attack.

The Cajon Valley Union School District, which is home to a very large immigrant and refugee population, mostly from Afghanistan and Iraq, will be offering counseling support to all students in need in the wake of recent events.

“Cajon Valley Union School District Community and Staff wait with open arms for the safe return of all of our families,” Shen said in a statement.

Shen on Wednesday said he believed that six CVUSD families were in Afghanistan, noting that the information is fluid and constantly evolving.

A total of 13,146 people have been evacuated from Afghanistan since the operation began on Aug. 13, the United Kingdom’s Foreign, Commonwealth and Development Office (FCDO) said on Thursday.

In a statement, the FCDO said the military operation — called Operation Pitting — has seen more than 1,000 members of the UK armed forces deployed to Kabul to assist in the evacuations.

This includes embassy staff, British nationals, those eligible under the Afghan Relocation and Assistance Policy (ARAP) program and a number of nationals from partner nations, the statement said.

At no point Thursday did President Joe Biden consider keeping any US forces in Afghanistan past the Aug. 31 deadline, despite the deadly attacks near the Kabul airport, White House press secretary Jen Psaki said.

Responding to a question from CNN’s Kaitlan Collins, Psaki said the President still believes all US forces should be out by the end of the month because that is what his military commanders are advising will be best for the US in the short and long term.

“There are several reasons for that. One is the ongoing threats and the second that that we want to be able to have the ability to get individuals out who have been partners of ours after the 31st and they believe the best way to do that is to stay on that timeline at this point in time,” she added.

Psaki would not say whether the White House still anticipates the mass-evacuation flights that US and coalition forces have been carrying out will end before Aug. 31.

“I'm not gonna get into an operational timeline of when the last evacuation flight will be and I don't expect the Department of Defense will do that either. We will let you know, as we have twice a day, as we have updated numbers,” she said.

Asked if there is an alternative plan being discussed on how to get people seeking to leave Afghanistan to the Kabul airport given it’s potentially dangerous to be waiting near the gates right now, Psaki said that there are “a range of operations and operational approaches that our commanders and military on the ground have been utilizing over the course of several days.” 

“I’m not gonna outline those from here, but that is why they're in touch with American citizens, why they’re in touch with partners we’re working to evacuate to get them safely to the airport and evacuated at the appropriate time,” Psaki said.

White House press secretary Jen Psaki provided a breakdown of when President Biden learned of the attack in Kabul that claimed the lives of 12 US service members and injured another 15.

"As the President arrived in the Situation Room, one of the first updates he received, of course, was about the attacks on the ground in Kabul," she added. "There were — this was a developing situation, as it has been through the course of the day and through the course of his briefing with his national security team this morning, his commanders on the ground also and in the region gave regular updates as they learned more information."

Psaki continued: "Once he left the Situation Room, those updates proceeded through the course of the day. He's been in constant contact with his national security adviser, his secretary of state, secretary of defense and military commanders both here and in the region."

Flags across the United States will be lowered to half-staff “as a mark of respect” for the victims of the terror attack in Afghanistan, the White House said.

Press secretary Jen Psaki said flags would lower on Thursday and stay lowered until sunset on Aug. 30 “in honor of the victims of the senseless acts of violence in Kabul, Afghanistan.” 

President Biden has not yet spoken to the families of the service members killed in Afghanistan, the White House said Thursday evening, pointing to the next-of-kin notification process still being underway.

“Until that process concludes,” Psaki said at an evening press briefing, “the President will not make a call because that’s the first step in the process.” 

She also left the door open to the President making the trip to Dover, Delaware, when the remains of the fallen service members return to US soil. 

President Biden said the US will try to evacuate some Afghan Special Immigrant Visa (SIV) applicants out of Afghanistan past the Aug. 31 deadline, but he did not guarantee their extraction.

Asked what his message is to those Afghans who can't make it to the airport by the deadline, Biden said: "We're going to try to continue to get them out. It matters."

President Biden said Thursday that he has ordered up plans to strike ISIS-K targets following the attack near the Kabul airport.

ISIS in Khorasan, known as ISIS-K, claimed that an ISIS militant carried out the suicide attack, but provided no evidence to support the claim.

US officials have been warning over the past week that a threat of a terror attack at the airport was becoming more acute. Earlier on Thursday local time, US diplomats in Kabul warned American citizens to "immediately" leave several gates into the airport, citing security threats.

But who are ISIS-K? ISIS-Khorasan is a branch of the terror group that first emerged in Syria and Iraq. While the affiliates share an ideology and tactics, the depth of their relationship with regards to organization and command and control has never been entirely established.

US intelligence officials previously told CNN the ISIS-K membership includes "a small number of veteran jihadists from Syria and other foreign terrorist fighters," saying that the US had identified 10 to 15 of their top operatives in Afghanistan. The group's name comes from its terminology for the area that includes Afghanistan and Pakistan: "Khorasan." 

The US Defense Department Inspector-General for Afghanistan (SIGAR) said in a report covering the months April to June of this year that "ISIS-Khorasan exploited the political instability and rise in violence during the quarter by attacking minority sectarian targets and infrastructure to spread fear and highlight the Afghan government's inability to provide adequate security."

ISIS-K has formed cells in Kabul which have carried out a number of devastating suicide attacks in and beyond the Afghan capital since 2016. 

The group has built up a presence in eastern Afghanistan in recent years, especially in the provinces of Nangahar and Kunar. Last August, the group attacked the main prison in Jalalabad, the capital of Nangahar, in an effort to free dozens of their supporters who had been captured by the Afghan army and police.

Read more about the group here.

CNN's Nikki Carvajal, Jim Sciutto and Tim Lister contributed reporting to this post.