Pakistani fighter jets Sunday bombed hideouts of Islamist militants for the second time in a week, killing over 50 insurgents in the country’s north-western tribal region, officials said.

The strikes in North Waziristan area targeted mud-houses used by Islamic Movement of Uzbekistan (IMU), a group whose fighters laid a deadly siege of country’s busiest airport on June 8.

A military statement said most of the dead were Uzbek nationals, believed to be behind a night-time attack at Karachi airport that killed about 40 people, including 10 attackers.

The militants from IMU have been based in Pakistan since they were driven out of Afghanistan by international forces in 2001.

“There were confirmed reports of the presence of foreign and local terrorists in these hideouts who were linked in planning of the Karachi airport attack,” the military said.

“Reportedly over 50 terrorists, mostly Uzbek foreigners, were killed in the strikes. An ammunition dump has also been destroyed.” The information could not be verified as the area is inaccessible to outsiders including journalists.

It was the second time in a week that militants’ hideouts had been bombed.

On Tuesday, at least 25 suspected militants were killed in air strikes in Tirah valley of Khyber tribal district near the Afghan border.

Last month, fighter jets killed more than 100 militants including some key Taliban commanders in the tribal area after a series of attacks against the military.

Violence has surged in Pakistan after a government effort to engage Taliban in a peace process ended without making any significant headway.