Pakistani security forces on Friday killed 11 militants during clashes in a lawless district near Afghanistan, one day after several hundred rebels staged a cross-border attack, officials said. The skirmishes took place in the Sarakai and Mukha areas northwest of Khar, the main town of Bajaur district where Pakistan has carried out a series of offensives against Taliban and other Islamist insurgents since August 2008. \"A group of militants attacked security forces and local lashkar (militia) during a joint search operation in the two areas, triggering a gunfight,\" local government official Mohammed Ilyas Khan told AFP. He said that at least 11 militants and one member of the lashkar were killed in the clashes. Khan said he did not know the nationality of the militants killed but said they had been hiding since Thursday\'s attack on a village in Bajaur. Local security officials confirmed the clashes and casualties. Five civilians and nine militants were killed in Thursday\'s clash, which Pakistani officials said was the third cross-border attack into the northwest this month, reportedly carried out by some 250-300 militants. Afghan police denied that the militants came in from Afghanistan. The border is porous and tensions between Afghans and Pakistanis are high over responsibility for Islamist militant strongholds in both countries. Pakistan has repeatedly claimed to have eliminated the militant threat in Bajaur, one of seven districts in the country\'s semi-autonomous tribal belt that the United States sees as the global headquarters of Al-Qaeda. Earlier this month, Pakistan conveyed \"strong concern\" to the Afghan ambassador to Islamabad, calling for \"stern action\" by Afghan and US-led NATO troops to crack down on militants in eastern Afghanistan.