ISI allocated the highest percentage of covert aid to warlord Gulbuddin Hekmatyar leader of the Hezb-e-Islami faction. This was based on his record as an effective anti-Soviet military commander in Afghanistan. The other reason was that Hekmatyar and his men had "almost no grassroots support and no military base inside Afghanistan", and thus more "dependent on Zia-ul-Haq's protection and financial largesse" than other mujahideen factions. In retaliation for Pakistan's assistance to the insurgents, the KHAD Afghan security service, under leader Mohammad Najibullah, carried out (according to the Mitrokhin Archives and other sources) a large number of operations against Pakistan. In 1987, 127 incidents resulted in 234 deaths in Pakistan. In April 1988, an ammunition depot outside the Pakistani capital of Islamabad was blown up killing 100 and injuring more than 1000 people. The KHAD and KGB were suspected in the perpetration of these acts. Soviet fighters and Democratic Republic of Afghanistan Air Force bombers occasionally bombed Pakistani villages along the Pakistani-Afghan border. The target of Soviet and Afghan fighters and bombers were Afghan refugees camps on Pakistan side of the border. These attacks are known to have caused at least 300 civilian deaths and extensive damage. Sometimes they got involved in shootings with the Pakistani jets defending the airspace.