Karachi, Pakistan (CNN) -- A U.S. drone Wednesday fired on an area in northwestern Pakistan, according to two Pakistani intelligence sources and a witness.
Details about what the drone hit and whether there were any casualties weren't immediately available.
Northwestern Pakistan is home to loosely governed tribal areas near the border with Afghanistan, and the area is a base for foreign fighters and a place of refuge for members of the Islamist militant Haqqani movement.
The drone strike comes just days after two brazen attacks on or near Pakistan's largest airport in the southern Pakistani port city of Karachi.
Earlier Wednesday, the Islamic Movement of Uzbekistan claimed that it carried out one of the attacks -- the weekend airport assault that resulted in an hours-long siege and left 36 people dead, including the assailants.
The claim was made in an e-mail that included pictures that the militant group said were of the 10 attackers.
The militants said the attack was carried out with the Pakistani Taliban, which has confirmed that members of the Islamic Movement of Uzbekistan conducted the Karachi airport attack, Pakistani Taliban commander Abdullah Bahar Mehsud told CNN in a phone conversation.
Mehsud said the pictures in the e-mail claiming responsibility were indeed photos of the 10 attackers. He said the Pakistani Taliban helped coordinate and provided material support in the attack.
Late Sunday night, 10 militants stormed the airport's cargo area in a siege that left dozens dead.
The Pakistani Taliban also claimed responsibility for that assault, saying the attack was retaliation for the death of former chief Hakimullah Mehsud, who was killed in a U.S. drone strike in November in North Waziristan.
The Uzbek militants have not claimed responsibility for a second attack Tuesday on airport security forces that forced the airport, Pakistan's largest and busiest, to shut down.
Tuesday's assault targeted the Airport Security Forces academy near Karachi's Jinnah International Airport, the airport's manager told CNN's Saima Mohsin in Karachi.
Security forces told CNN that an unknown number of gunmen attacked the academy's entrance and were met with an armed response. The attackers fled, and no one was killed in the attack, officials said.
Once again, the Pakistani Taliban, which is formally known as Tehreek-i-Taliban Pakistan, or TTP, claimed responsibility.
"This wave of attacks will be continuing in retaliation for the shelling and atrocities of the government," spokesman Shahidullah Shahid said by phone Tuesday from an undisclosed location.
Shahid said earlier this week that the Pakistani Taliban would engage "in a full-out war with the Pakistani state, starting on June 10."
But the airport itself was safe Tuesday, Pakistan's Civil Aviation Authority said.
"#Jinnah Airport is safe, #ASF academy is under attack," the aviation authority tweeted Tuesday.
The Civil Aviation Authority said flights were temporarily suspended but later resumed Tuesday.
By Tuesday afternoon, the situation was "under control," military spokesman Asim Bajwa said.
"3 to 4 terrorists fired near ASF Camp, ran away," Bajwa tweeted. "No breach of fence, no Entry. Chase is on, situation under control."
Airstrikes killed 15 militants
Hours before the renewed violence in Karachi, the Pakistani military launched a deadly assault targeting nine militant hideouts Tuesday.
At least 15 militants were killed in the airstrikes on Khyber Agency, in tribal areas bordering Afghanistan, the Pakistani military said.
A military spokesman said he could not confirm whether the airstrikes were directly related or in response to the airport violence this week.
But it's those kinds of strikes that the Pakistani Taliban warned would spur more violence from their end. When the TTP claimed responsibility for Sunday's airport attack, it called on the government to end airstrikes -- or face more attacks like the Karachi airport terror attack.
Apparently, the TTP followed through with its promise.
History of terror
The Pakistani Taliban has long conducted an insurgency against the Pakistani government.
"Their primary target is the Pakistani state and its military," said Raza Rumi of the Jinnah Institute, a Pakistani think tank.
"It resents the fact that (Pakistan) has an alliance with the West, and it wants Sharia to be imposed in Pakistan."
The U.S. Justice Department charged former TTP chief Hakimullah Mehsud in 2010 for his alleged involvement in a 2009 bombing at the United States' Forward Operating Base Chapman in Khost, Afghanistan. The attack killed seven U.S. citizens, including five CIA officers and a member of Jordanian intelligence.
Hakimullah Mehsud took over from Baitullah Mehsud, a fellow clan member, in 2009 after the latter was killed in a U.S. drone strike. Four years later, Hakimullah Mehsud suffered the same fate.
CNN's Sophia Saifi reported from Karachi; Holly Yan reported and wrote from Atlanta. Journalists Saleem Mehsud, Zahir Shah and Adeel Raja also contributed to this report.