LAHORE, Pakistan -- A suspected Islamic militant walked into a crowd of police guarding a courthouse and blew himself up yesterday, killing 24 others and wounding dozens in the first major attack in Pakistan since the assassination of Benazir Bhutto.

The blast at Lahore High Court, minutes before a planned anti-government rally by lawyers, was a bloody reminder of the security threats facing this key U.S. ally ahead of Feb. 18 parliamentary elections.

Suicide attacks have become as commonplace in Pakistan as in neighboring Afghanistan, adding to rising pressure on President Pervez Musharraf as he struggles to stay in office eight years after seizing power in a military coup.

At least 20 suicide bombers have struck during the past three months in attacks that killed 400 people, many of them from the security forces -- the most intense period of terror strikes here since Pakistan allied with the U.S. in its war against al-Qaida and other extremist groups in 2001.

Police said the attacker was in the middle of about 70 officers in riot gear and detonated explosives on his body. All but three of the dead were police officers.

There was no claim of responsibility. The government has blamed previous attacks on Islamic radicals allied with al-Qaida and the Taliban who are intent on expanding their reach from strongholds in Pakistan's lawless tribal region along the Afghan border.

Musharraf blamed the same militants for the Dec. 27 attack that killed Bhutto, a secular former prime minister who had repeatedly pledged to battle Islamic extremism in Pakistan.

The attack occurred about 15 minutes before lawyers planned to demonstrate in front of Lahore's courthouse as part of a nationwide protest movement against Musharraf for the November ouster of independent-minded Supreme Court judges who could have ended his rule.

Musharraf condemned the latest bombing and reiterated his resolve to fight terrorism, saying he was "not to be deterred by such acts," the state news agency reported.

The attack came on the eve of the Islamic month of Muharram, which often is marred by bombings and clashes between Pakistan's Sunni Muslim majority and its Shiite minority.