Islamic fundamentalists burned tires, blocked transit routes and clashed with police in a nationwide strike Friday to protest the president's pro-U.S. policies on Afghanistan. Three demonstrators were killed in the central city of D.G. Khan.

The confrontations were the most serious in recent weeks, with police rounding up scores of protesters in several cities. Organizers called the strike a success, claiming it shut down major cities across Pakistan and drew thousands of demonstrators to rallies.

However, the overall effect was difficult to gauge since government offices and schools ordinarily shut down Friday after midday prayers. The one-day strike reflected the anger among Islamic groups but did not pose a major threat to President Pervez Musharraf's military government.

The Afghan Defense Council, an alliance of 35 Islamic groups, organized the strike to denounce Musharraf and to express support for Afghanistan's Taliban rulers.

"After today's successful strike, Musharraf has no right to remain in power ... and he should step down," Maulana Samiul Haq, head of the council, told several thousand demonstrators in the northwestern city of Peshawar.

Haq, who runs an Islamic seminary that many Taliban leaders attended during the 1980s when they were war refugees, warned of a "civil disobedience movement" if Musharraf continued to support the U.S.-led campaign in Afghanistan.

Violence broke out in D.G. Khan, 300 miles south of Islamabad. Some 1,000 protesters blocked railway tracks and the main highway, throwing stones and firing shots when police tried to remove them, authorities said.

Police responded with live fire, killing three protesters and wounding six, according to officials. All were supporters of Jamiat Ulema-e-Islam, a radical Islamic movement whose leader, Fazle ur-Rehman, is being detained in a government guest house.

In the volatile port city of Karachi, police fired tear gas to disperse some 2,000 demonstrators who threw stones and tried to block main roads.

Pakistani authorities also arrested some 500 activists throughout the country in overnight raids in an attempt to limit the scale of the protests, government officials said. They were expected to be released Friday evening.

Islamic groups have been staging protests every Friday for the past two months. Shortly after the Sept. 11 terror attacks in the United States, Musharraf abandoned Pakistan's support for the Taliban and sided with the United States in its fight against global terrorism.

Several of the early protests were violent, but they have been peaceful in recent weeks, and the size of the crowds has diminished.

Attempting to take some of the momentum out of Friday's strike, the government also declared the day a public holiday marking the birthday of Mohammad Iqbal, a philosopher and poet who called for the creation of Pakistan in 1930.

Streets in the major cities of Karachi, Lahore, Peshawar and Rawalpindi were much quieter than usual for a Friday. It was not clear how much was linked to the holiday, and how much was attributable to the strike call.

In Islamabad, a city of government officials, foreign diplomats and well-to-do businessmen, protests have been rare and shops normally remain open on Fridays. But most shops were closed.

Musharraf's government has tolerated marches and rallies, but has also arrested leaders of religious parties who have called for the ouster of his military government.

Pakistan's Interior Minister Moinuddin Haider said Thursday that the government has allowed religious parties to express their views, but "nobody will be allowed to disrupt law and order."

"We will be very tough with the law violators," he said.