Story highlights

NEW: ISIS says 3 "Caliphate soldiers" carried out the Jalalabad attack and that one of them escaped

NEW: ISIS says scores of Pakistanis died; Pakistan says 7 Afghans died and just one Pakistani official was injured

U.S., Afghanistan officials have warned about ISIS' rise in Afghanistan

Kabul, Afghanistan CNN  — 

ISIS claims it is behind a bloody attack Wednesday outside a Pakistani Consulate in eastern Afghanistan – one that killed seven Afghan security forces and hinted at the terror group’s spiraling reach and ambition.

In a statement distributed on ISIS-affiliated media, the group said that three “Caliphate soldiers” stormed the consulate in Jalalabad during what it called a four-hour-long mission. It said that “scores” of consulate personnel and “apostate Pakistani intelligence officers” died in the operation and that one attacker escaped. But the Afghan and Pakistani governments said that all three attackers and seven Afghan forces died, but no Pakistani officials did.

CNN could not verify the authenticity of the ISIS claim, which surfaced on social media, nor could it iron out the discrepancies in the accounts.

ISIS emerged in Iraq and Syria, where it holds swaths of territory as part of what it calls its Islamic State caliphate. It has since carried out or inspired attacks elsewhere in the Middle East, Asia, Europe and North America. If its latest claim is legitimate, it shows the extremist group flexing its muscles in the war-torn region.

And by striking near a Pakistani diplomatic mission, it’s targeting two countries, not just one.

For years, Afghanistan has faced down many militant organizations, with the Taliban and al Qaeda foremost among them. Yet ISIS has become more formidable in that country and neighboring Pakistan over the past year, thanks to an influx of Taliban defectors.

Without specifying who is to blame, Pakistan’s Foreign Office did “strongly condemn” Wednesday morning’s “terrorist attack” and urged its western neighbor to respond.

“The government of Afghanistan has been requested to thoroughly investigate the incident and bring the culprits to book,” a Pakistani statement said. “(It) has also been requested to ensure (the) safety and security of Pakistan missions in Afghanistan and our officials working there.”

Official: 10 wounded, including 3 civilians

The bloodshed began around 9 a.m. (11:30 p.m. ET Tuesday) when a suicide car bomb detonated around an Afghanistan police vehicle, said Ataullah Khogyani, a spokesman for the governor of eastern Nangarhar province.

That blast cleared the way for two other attackers to enter an empty government guesthouse close to the Pakistani Consulate. They waged a more than two-hour-long gun battle (not four, as ISIS claimed) from there that ended with both armed assailants killed.

By that point, the seven Afghan security forces were also dead.

At least 10 others, including three Afghan civilians, were wounded in the battle.

Pakistan’s Foreign Office said that all its officials are safe, with one suffering only a slight injury from broken glass.

Disaffected Taliban swell ISIS’ ranks

Afghanistan is no stranger to such violence. The Asian nation has been mired in war, off and on, for decades – from the 1980s battles between Islamist Mujahideen and Soviet-backed forces, to the 1990s civil war, to the bloodshed that followed the U.S.-led invasion after the September 11, 2001, terrorist attacks.

Still, ISIS is a relatively new player. In March, when CNN first reported about ISIS’ recruiting efforts in Afghanistan, Afghan President Ashraf Ghani warned the U.S. Congress about the “terrible threat” the group poses to his country and its neighbors.

“Terrorists neither recognize boundaries nor require passports to spread their message of hate and discord,” Ghani said.

Referring to Afghanistan and Pakistan as Khorasan, ISIS has been up front in its words and actions about fomenting terror and establishing its grip in the volatile region.

Many of ISIS’ new recruits are disaffected Taliban. This fact may have played into Russia and the Taliban sharing intelligence pertinent to the fight against that terror group, as related by Russian Foreign Ministry spokeswoman Maria Zakharova.

The group has boasted about its role in violence, like a man killing 33 by setting off a bomb while on his motorbike in front of a bank in Jalalabad, the same city where Wednesday’s attack occurred. More recently, ISIS kidnapped then beheaded seven members of the Hazara ethnic minority in Zabul province.

The commander of U.S. forces in Afghanistan told Congress last fall that between 1,000 and 3,000 active ISIS members were in Afghanistan.

“In the last year, we have observed the movement’s increased recruiting efforts and growing operational capacity,” said Gen. John Campbell.

CNN’s Masoud Popalzai reported from Kabul, and CNN’s Greg Botelho reported and wrote from Atlanta. CNN’s Hamdi Alkhshali, Sophia Saifi and Ed Payne contributed to this report.