A suicide bomber blew himself up among worshippers streaming toward a Shiite Muslim mosque in central Pakistan on Thursday, killing 24 people and wounding dozens more.
The attack in the city of Dera Ghazi Khan risks sparking sectarian fury in a country already battling rising militancy along the Afghan border and tension with India over the Mumbai terrorist attacks.
The bomb detonated as a crowd approached the mosque for an evening prayer ceremony. Television footage showed bystanders and emergency workers trying frantically to help victims lying in the darkened street.
Athar Mubarak, the city police chief, said the bomb contained metal balls and nails. As well as the 24 dead, another 40 people were wounded, he said.
"Evidence collected from the spot indicates that a suicide bomber blew himself up in the crowd," Mubarak said.
"According to eyewitnesses, nothing was thrown from outside," said Jawed Mehmood Bhatti, a district government official. "It looks as if someone was standing at the site of the blast and waiting for the procession and he blew himself up as the procession came close to him."
Hasan Iqbal, the city's top administrator, said he believed that the Shiite gathering was deliberately targeted. He wouldn't say whether Sunni extremists were likely behind it and there was no immediate claim of responsibility.
However, relations between this Muslim nation's strong Sunni majority and Shiite minority have already been tested by a series of attacks attributed to sectarian extremists.
Much of the violence has been in Pakistan's northwest, where the Taliban and other violent Sunni groups have gained ground.
In the deadliest recent incident, a car bomb killed 29 people and wounded scores near a Shiite mosque in the regional capital, Peshawar, in December. On Tuesday, a grenade attack killed at least one person at a Sunni mosque in the town of Dera Ismail Khan.
Pakistan is under pressure to clamp down on a string of Islamist extremist groups, including one suspected by archrival India and in Western capitals of being behind the November attacks in Mumbai that killed killed 164 people and nine assailants.