(CNN) -- Pakistani military forces clashed Friday with Islamic militants in mountainous northwest Pakistan, in battles that left at least 90 militants dead and four military personnel wounded, a military spokesman told CNN.
Pakistani soldiers stands guard at a post in Pakistan's Wana tribal district of South Waziristan.
The militants gathered around the Ladha Fort in South Waziristan -- a tribal territory in Pakistan -- early Friday morning, and fired rockets into the fort, according to military spokesman Lt. Col. Baseer Haider Malik.
Malik said the military used artillery and small arms fire to disperse them, killing 20 to 30 militants.
In a separate incident elsewhere in South Waziristan, militants attacked a convoy of security forces with rockets and small arms fire, Malik said. The Pakistani forces retaliated with rockets and small arms fire, killing 50 to 60 militants, Malik said.
Four security personnel were wounded in the hour-long fight, Malik said, and two army vehicles were damaged.
South Waziristan is said to be a stronghold of Taliban warlord Baitullah Mehsud -- the man the Pakistani government has named a prime suspect in the December 27 assassination of former Prime Minister Benazir Bhutto.
Pakistan has attempted to crack down on the largely lawless tribal areas along the Afghan border under U.S. pressure. A U.S.-led invasion overthrew the Taliban after al Qaeda's September 11, 2001, attacks on New York and Washington, but American and allied troops are now battling a resurgence of the fundamentalist Islamic militia in Afghanistan's south.
Earlier this week, militants abandoned another fort in South Waziristan they overran during a pitched battle Wednesday, Maj. Gen. Athar Abbas, a military spokesman, said. The militants left later that day without another firefight with Pakistani forces, Abbas told CNN.
The battle for the control of the border fort killed at least seven of 40 Pakistani troops stationed there. Fifteen others fled and 18 border guards were initially reported missing.
Abbas said five of the missing guards were apparently located in a nearby village, but his men had not yet confirmed the report.
The militants breached the walls of the colonial-era outpost along the Afghan border with explosives and seized the fort after a firefight that lasted about 12 hours, Malik said.
An estimated 250 to 300 or more fighters armed with rifles and rocket-propelled grenades took part in the Wednesday assault against a garrison of 40 members of Pakistan's paramilitary Frontier Corps, Malik said. E-mail to a friend