A suspected suicide bomb exploded at a Shia Muslim mosque packed with worshippers in the Pakistani biggest city of Karachi killing at least 13 people and wounding scores of others.
President Pervez Musharraf condemned the blast as a "heinous act of terrorism" and ordered an immediate investigation to trace the culprits.
The attack occurred shortly at a mosque inside a government-run religious school, shattering windows and pockmarking the walls with shrapnel and splattered blood.
The school, which houses students aged four to 18, has separate mosques for Sunni and Shia Muslim worshippers. Witnesses said the school had let out early, as it normally does on Fridays. Most of the victims were adults who came to the mosque for prayers.
Doctors said 12 dead were brought to Karachi's Civil Hospital, and that there were 215 wounded, of which 45 were admitted. Most of the rest were released after treatment for minor injuries or had been transferred to other hospitals.
A police explosives expert said he had found no timing or radio devices, indicating it may have been caused by a suicide bomber.