At least 60 people were killed and 150 wounded on Friday when gunmen opened fire indiscriminately on crowds in the southern Pakistani city of Hyderabad, hospital doctors and witnesses said.
An indefinite curfew was clamped on the city and its satellite town of Latifabad, the official APP news agency said.Large numbers of troops moved into the town, the second biggest city in Sind Province, to enforce the curfew, witnesses said.
The motive for the attack was not immediately clear. Before Friday's attack, more than 60 people had been killed in Hyderabad since June in ethnic fighting between native Sindhis and Mohajir immigrants.
The gunmen attacked simultaneously in four or five different places in the city in the evening on Friday, the weekly rest day in Moslem Pakistan, the witnesses said.
In one area, a small van crammed with heavily armed gunmen stopped outside a cinema and opened fire on people on the streets. Four were killed and another injured.
The independent news agency PPI said five people in a wedding party from Karachi were killed in another attack.
Doctors said at least 60 people had been killed and the death toll was likely to rise as many of the injured were badly hurt.
The hospitals issued urgent appeals for blood donors, but people were hampered from coming forward by the curfew.
Some 550 people have died in ethnic riots in Sindhi cities over the past two years. But the bulk of the fighting has been in Karachi, 110 miles west of Hyderabad and with more than seven million people the biggest city of Pakistan.
Until last June the clashes were almost entirely between the Mohajirs - Moslems who migrated from other parts of British India at independence and partition in 1947 - and Pashtuns from northwest Pakistan.
But tension grew between the Mohajirs, a largely middle-class community asserting its political muscle, and Sindhi nationalists.