Pasitani police fired tear gas at protesters who were demanding President Pervez Musharraf step down — a sign of rising tensions ahead of parliamentary elections next month that many predict will weaken the former army commander's grip on power.

"This country is going into deep crisis and it's all because of one man — Musharraf," said protester Fatimah Ihsan. "He must go."

Pakistani troops backed by helicopters and artillery attacked suspected militant hide-outs in tribal areas close to the Afghan border, killing 40 rebels and arresting 30, the army said Thursday. At least eight soldiers also died.

The fighting took place in South Waziristan, a militant stronghold where the rebel leader accused by the CIA and Pakistan's government of masterminding last month's assassination of opposition leader Benazir Bhutto is believed to be hiding.

The militants were killed in a series of raids Wednesday and early Thursday in the mountainous region, the military said.

Three districts in South Waziristan "had been cleared of militant strongholds and hide-outs" as a result of the operations, the military said in a statement, adding that 40 rebels had been killed and 30 others arrested.

Eight soldiers also died, it said, giving no more details.

South Waziristan is a semiautonomous tribal region where the central government has never had much control. It is home to scores of Al Qaeda and Taliban fighters who fled from neighboring Afghanistan after the U.S.-led invasion there in 2001.

Surging violence in the region and a series of bloody suicide bombings against security forces around the country have added to pressure on Musharraf, who took power eight years ago in a military coup and allied himself with the United States following the Sept. 11, 2001 terrorist attacks there.

The scuffles in Islamabad took place close to the house of the ousted Supreme Court chief justice, Iftikhar Mohammed Chaudhry, who has been held incommunicado since Musharraf declared a state of emergency Nov. 3.

About 250 lawyers and other anti-government activists rallied there to demand his release, shouting "Go Musharraf go!" as they tried to push their way through a maze of barbed wire and a cordon of riot police. Police fired tear gas at the protesters, who responded with volleys of stones. There were no reports of injuries or arrests.

Nawaz Sharif, a former prime minister who returned from exile in November to lead a campaign against Musharraf, accused him of failing to bring peace in the tribal regions.

"The problem in the tribal regions will not be solved through the use of bullets, guns and gunship helicopters, but we need to win the hearts and minds of people there," Sharif told reporters in Peshawar, the capital of neighboring North West Frontier province.

The Pakistani leader has come under increasing pressure since Bhutto's assassination after her return home from eight years in exile to run in the elections, in which her party was widely expected to do well.

Opposition leaders have accused the government and intelligence agencies of complicity in the Dec. 27 attack.

Musharraf has blamed militants acting on behalf of Al Qaeda for the killing. He has rejected calls for an independent, U.N.-led international inquiry, but has allowed a team of detectives from Britain's Scotland Yard to assist government investigators.

On Wednesday, the New York-based group Human Rights Watch urged the British government to pull Scotland Yard from the "flawed Pakistani investigation."

"Pakistan's investigation into Bhutto's murder lacks independence, transparency and credibility," it said. "Scotland Yard ... should not tarnish its reputation by lending its imprimatur to this dubious inquiry."

The group urged the U.S., Britain, and other countries to press Pakistan to accept a U.N. probe.