A suicide bomber blew himself up among police deployed outside a court in eastern Pakistan ahead of a planned anti-government protest Thursday, killing at least 22 people and wounding dozens more, officials and witnesses said. The blast in front of Lahore High Court was the latest in a wave of attacks targeting politicians and security forces ahead of the February 18 parliamentary elections. There was no immediate claim of responsibility, but suspicion will likely fall on militants linked to Taliban and al-Qaida. It came as Scotland Yard investigators visited forensic laboratories elsewhere in Lahore, the capital of Punjab province, to examine evidence in the assassination two weeks ago of opposition leader Benazir Bhutto in Rawalpindi, a garrison city to the north. "I have not heard such a big explosion in my life. We felt as if our ear drums were about to burst," said Abdul Hameed, a lawyer's assistant who was inside the court when the bomber struck. The blast shattered windows in the court house and set off volleys of tear gas shells carried by the police, preventing people getting close to the victims in the seconds after the attack, witnesses said. Lahore chief of police operations Aftab Cheema said the bomber had run up to a barrier manned by police and blew himself up. He said 20 policemen and two civilians were killed. More than 50 others were wounded, including civilian passers-by, officials said. "It was a suicide attack," Lahore police chief Malik Iqbal told Dawn News TV. He said police were "definitely" targeted. The police had been deployed in front of the court ahead of a planned anti-government protest by lawyers that was due to start about 15 minutes before the bomb went off. About 200 lawyers were inside the High Court at the time of the blast, and others were marching from a nearby district court. Police cordoned off the area and appealed to bystanders to rush to hospitals to donate blood instead of crowding the scene and hindering emergency services. President Gen. Pervez Musharraf condemned the attack and reiterated his resolve "to continue the fight against terrorism and extremism and not to be deterred by such acts," the state Associated Press of Pakistan news agency reported. The government of Musharraf, a key ally in the US-led war on terror, has blamed two Taliban commanders linked to al-Qaida for a wave of about 20 suicide attacks that have killed about 400 people in the past three months, many targeting security forces. On December 27, Bhutto and about 20 others were killed in a gun and suicide bomb attack after addressing an election rally. The murder of the two-time prime minister sparked days of rioting that left dozens more dead and forced a six-week postponement in the elections which are meant to bring a new era of democracy after eight years of military rule under Musharraf. Her party has accused elements of the ruling pro-Musharraf party of plotting to kill Bhutto, which the government vehemently denies. Thursday's attack comes ahead Islamic month of Muharram, which is often marred by bombings and fighting between Pakistan's Sunni Muslims and its Shi'ite minority. Authorities have already boosted security at holy sites across the country.