An explosion on Friday tore through a house in Karachi, Pakistan's largest city, killing at least six suspected militants, police said, DPA reported.
The house, located in the Baldia Town neighbourhood, collapsed in the blast, believed to have been caused by explosives stored in the building.
"It seems to be a premature explosion that killed six people," Karachi police chief Waseem Ahmad said.
Police suspected that those killed were members of a militant group planning terrorist attacks in the country's financial capital.
Interior Minister Rehman Malik told reporters that the house was occupied by man from Pakistan's Swat valley, where the security forces launched an operation last spring to quell the Taliban insurgency.
More than 2,000 militants were killed in the first two months of intense fighting. Sporadic clashes continue as troops carry out operations to eliminate remaining pockets of resistance.
Malik said some other people, also from Swat, arrived at the house at 3 am (2200 GMT Thursday) and were accommodated in a corridor, where the explosion took place at about 7:45 am (0245 GMT).
Television footage showed bodies partially buried under the rubble.
An unexploded suicide vest, several hand grenades and a Kalashnikov assault rifle with spare magazines were seized from the ruins.
The blast came after a bomb went off last week in Karachi at a religious march by minority Shiite Muslims, killing dozens.
Pakistan has been hit by a wave of bombings since October when nearly 30,000 soldiers began a major offensive against the Taliban and al-Qaeda militants in their stronghold of South Waziristan near the Afghan border.
These assaults have killed over 600 people in the last three months.