Gunmen wearing suicide vests stormed two Pakistani mosques belonging to a minority sect in Lahore, bringing carnage to Friday prayers and killing around 80 people, officials said.
Squads of militants burst into prayer halls firing guns, throwing grenades and taking hostages in the deadliest attack on the city of eight million, which has been increasingly hit by Taliban and Al-Qaeda-linked violence.
Both mosques belonged to the Ahmadi community, which Pakistan has declared non-Muslim. Although the estimated minority of two million has been attacked by Sunni extremists before, the magnitude of yesterday's assault was unprecedented.
Pakistan's leading rights group said the community had received threats for more than a year and officials blamed the attack on Islamist militants, who have killed more than 3,370 people in bombings over the past three years.
"Terrorists have attacked mosques. They are firing and using grenades. They have taken people inside the mosque hostage," district civil defence official Muzhar Ahmed told AFP from the scene in the bustling neighbourhood Garhi Shahu.
The attacks sparked more than two hours of gun battles with police and commandos, as bursts of heavy gunfire rocked the neighbourhoods and rescue services raced through the streets to tend to the victims.
"The prayer leader was delivering a sermon inside the hall when I suddenly heard distant gunshots," Bilal Ahmed, a worshipper said after fleeing with his life from the mosque in Model Town.
"Then the firing became louder and closer and people started running here, there and everywhere to save themselves. Gunmen had entered the prayer hall and they were moving towards upper floors.
"The attackers were youths with beards who were not covering their faces. The floor was full of blood and broken glass," Mr Ahmed said.
As the gun battles ended in both locations, officials spoke of scenes of carnage - particularly in Garhi Shahu where dozens of bodies were found.
"Around 80 people have been killed," Sajjad Bhutta, the top city administrative official in Lahore, told reporters.
Doctor Rizwan Nasir, head of the rescue services in Lahore, said 108 people were wounded as police continued to search for any remaining attackers.
Taliban and Al-Qaeda-linked militants have orchestrated a three-year bombing campaign in Pakistan to avenge military operations and the government's alliance with the United States over the war in neighbouring Afghanistan.