Reuters

Mingora, May 6: Pakistani forces attacked Taliban fighters in the Swat valley with artillery and helicopters on Wednesday after the United States called on the government to show its commitment to fighting militancy.

Expanding Taliban influence in nuclear-armed Pakistan has spread alarm at home and abroad and will be a core issue when US President Barack Obama meets his Afghani and Pakistani counterparts in Washington later on Wednesday.

A February peace pact aimed at ending Taliban violence in Swat is in tatters and thousands of people fled from Mingora, the region's main town, on Tuesday after a government official said fighting was expected.

The militants have captured several important government buildings in the town, 130 km northwest of Islamabad, and took positions on rooftops.

While a curfew kept people off the streets, government forces attacked in and around the town, including at an emerald mine the Taliban have taken over.

"Security forces have engaged militants' positions at an emerald mine and helicopter gunships are also being used to flush militants out of Mingora," said a military spokesman.

A military official, who declined to be identified, brushed off speculation the clashes signaled an imminent offensive in Swat but residents said they saw troops being trucked in and a government official also said reinforcements were arriving.

The provincial government has warned 500,000 people could flee from the valley, which has a population of nearly 2 million.

Several hundred thousand have already fled fighting in different parts of the northwest since August, putting an extra burden on an economy propped up by a $7.6 billion International Monetary Fund loan.

Pakistani stocks have been hurt by security worries in recent months but the main index was more than 2 percent higher by midday Wednesday.

'Unwavering commitment'

President Asif Ali Zardari, former prime minister Benazir Bhutto's widower, is due to meet Obama and Afghanistan President Hamid Karzai for talks on the militant threat.

Obama will urge the leaders to put aside a history of mistrust and join Washington in an alliance against extremists, US administration officials said.

Pakistani action against militant enclaves on the Afghan border is vital to efforts to stabilise Afghanistan.

But increasing violence and the spread of the Taliban in Pakistan have raised doubts about the ability of the civilian government elected last year 
to deal with the threat.

"Pakistan must demonstrate its commitment to rooting out al-Qaida and the violent extremists within its borders," Richard Holbrooke, US special representative for Afghanistan and Pakistan, said in congressional testimony on Tuesday.

Foreign office spokesman Abdul Basit said Pakistan's commitment was unwavering: "We are suffering the most because of terrorism. Who else would be more interested in extirpating this menace?"

Afghanistan President Karzai said on Tuesday that Pakistan -- whose intelligence services have long been accused of maintaining old ties to the Afghan Taliban for strategic reasons -- should sever such links. Basit said the neighbours needed to transcend such old suspicions.

A Pakistani security analyst said the talks in Washington should at least improve understanding. What Pakistan gets out of it will depened on how forcefully it puts its case.

"We're being blamed for the cross-border movement (of militants to Afghanistan) but when we say 'increase the number of military posts on your side or fence the border or do selective mining', they don't agree," said the analyst, Nasim Zehra.

Some Mingora residents said they faced dwindling supplies of food and were desperate to get out.

"We are very scared. We want to go as soon as possible but can't because of curfew," said grocery shop worker Gul Nazir.

"We're running out of food. We don't know what to do."

The Swat peace pact, under which authorities agreed to a Taliban demand for introduction of Islamic sharia law in the former tourist valley, led to accusations from critics the government was caving in to militant aggression.

The Taliban refused to give up their guns and last month pushed into Buner district, only 100 km (60 miles) northwest of Islamabad, and another district adjacent to Swat.

With worry intensifying, security forces launched an offensive to expel militants from Buner and another district on April 26. About 180 militants have been killed, according to the military, although there has been no independent confirmation.

Critics say Pakistan has been in denial about the Taliban threat in a country where old rival India has long been the enemy and where militants have been used as "strategic assets" since the battle against Soviet occupiers in Afghanistan in the 1980s.