Pakistan ? A powerful suicide explosion killed at least 15 people and injured dozens of others Sunday evening, shortly after a large protest rally marking the one-year anniversary of the government forces’ raid on a radical mosque. Most of the dead were police officers.

The blast, which appeared to have targeted the security forces, poses a sharp new challenge to Pakistan’s coalition government, which has been struggling in its efforts to formulate a policy for dealing with Islamic militants.

The explosion occurred just before 8 p.m. local time at a police post close to a popular market and only a few blocks from the Red Mosque, which last summer became a hotbed of militant activity in the heart of the capital. President Pervez Musharraf, who, at the time, was also the leader of Pakistan’s military, sent in elite commandos to capture the mosque, a confrontation that left more than 100 people dead.