KARACHI, Pakistan — A suicide bomber struck a procession marking a key Shiite Muslim holy day in Pakistan's biggest city Monday, killing 30 people and wounding 60 in an attack blamed on extremists trying to hamper the country's fight against militancy by sparking a sectarian war.
Outraged Shiites responded to one of the worst sectarian attacks in the country this year by setting fire to buildings and vehicles at the blast site and pelting security forces with stones, a sign of frustration by the minority sect, which has suffered frequent attacks by Sunni extremist groups who regard them as heretical.
Authorities said these sectarian groups have teamed up with Taliban and al-Qaida militants waging war against the government in a joint effort to destabilize Pakistan. More than 500 people have been killed in attacks since mid October when the army launched a major anti-Taliban offensive in the country's northwest.
"A deliberate attempt seems to be afoot by the extremists to turn the fight against militants into a sectarian clash and make the people fight against one another," said President Asif Ali Zardari in a statement.
The southern city of Karachi has largely been spared the Taliban-linked violence that has struck much of the rest of the country, a fact that analysts believe is driven by the group's tendency to use the teeming metropolis as a place to rest and raise money. But the city has been the scene of frequent sectarian, ethnic and political violence.
The suicide bomber who struck Monday targeted thousands of Shiites marching through the streets to observe Ashoura, the most important day of a monthlong mourning period for the seventh century death of the prophet Mohammed's grandson, Imam Hussein. Ashoura was celebrated in other parts of the Muslim world on Sunday.
Karachi police Chief Waseem Ahmad said police were investigating the possibility that a second suicide bomber was also involved in the attack.
The blast killed 30 people and wounded 60, said Sagheer Ahmad, the health minister in Sindh province, where Karachi is the capital.
No group has claimed responsibility for Monday's attack, but Interior Minister Rehman Malik pointed his finger at a cluster of militant groups, including the Pakistani Taliban, al-Qaida, Lashkar-e-Jhangvi and Jaish-e-Mohammad, that he said have a joint goal to destabilize Pakistan.