Violence first erupted in the mountainous region on March 19 when a Taliban commander-turned-government supporter ordered foreign insurgents led by wanted rebel Tahir Yuldashev to disarm, leaving 160 people dead last week.

"Fifty-four people were killed today, two were yesterday. They include 45 foreigners," Interior Minister Aftab Sherpao told AFP.

"The fighting is going on, it intensified today after peace talks failed. Tribes are insisting on their demand that these people either surrender or quit the area."

The government says the latest developments reflect the success of its policy to encourage local tribesmen to expel foreign Islamic extremists, instead of costly and politically damaging army operations.

Local sources were not immediately able to confirm the death toll given by Sherpao, although communications in South Waziristan are poor because of the fighting. Last week they gave lower figures than Pakistani authorities.

Earlier a security official said tribesmen overnight seized control of a school which the foreigners were using as their base in Ghawakha, a town near Wana, killing seven Uzbeks.

Another official said three tribal fighters were also killed and six wounded in the fighting. Residents said the militants also shot dead a local man who was travelling in the area on his motorbike.

The latest clashes were concentrated in the mountainous Azam Warsak, Shen Warsak and Kalusha areas of South Waziristan. Residents say between 300 and 500 Uzbeks and Chechens are holed up in the area.

The Uzbeks were effectively under siege in the mountainous terrain as all roads leading to the troubled towns were being controlled by tribal commander Mullah Nazir, whose men are said to number around 1,500, they said.

A tribal leader, Haji Sharif, late Thursday ruled out any negotiations with the foreigners.

"We gave them shelter under our traditional Pashtun hospitality but they misused it and killed our people including tribal leaders," he said.

"We advised them to change their behaviour but they did not listen. Now we cannot tolerate them on our soil."

Thousands of al-Qaeda and Taliban militants fled into Pakistan's tribal areas after the fall of the fundamentalist Taliban regime in Afghanistan in late 2001.

Yuldashev, the Uzbek leader, was formerly a close confidant of al-Qaeda leader Osama bin Laden, officials say.

The government has signed a series of peace deals to get Pakistani tribesmen, many of whom previously offered shelter to the militants, over to its side. The first such deal was in South Waziristan in 2005.