Blast kills 7 at alleged militant den in Karachi

An explosion flattened a house being used by militants in Pakistan's financial capital Karachi on Friday, with seven people killed when bomb-making materials detonated accidentally, police said.

Guns, grenades and suicide vests were recovered from the house in the poor Baldia Town neighbourhood, while bodies were buried under the rubble as bomb disposal experts worked cautiously to clear the site.

"At least seven people were killed in the explosion," senior police official Abdul Majeed Dasti told AFP. "We have pulled out six bodies from the rubble while efforts are underway to recover the seventh body."

He said hand grenades, a Kalashnikov rifle and suicide vests were found at the scene, while city police chief Waseem Ahmad said the explosives appeared to have been detonated unintentionally.

"It seems that explosives which were stored in the house caused the explosion," Ahmad said.

"The house was being used by terrorists. We are taking utmost care in removing the rubble. Bomb disposal officials have arrived at the scene."

Interior Minister Rehman Malik said the people living in the house were from Swat, a northwestern valley where the military launched an operation last year to quash a two-year uprising by Taliban fighters.

"According to reports they were all asleep in the courtyard when this blast occurred," the minister told reporters in Karachi.

Suicide bombings and attacks by the Taliban and other Islamist militant groups have intensified in recent months as the military pursues an aggressive offensive to quash insurgent strongholds near the Afghan border.

Forty-three people were killed in Karachi -- Pakistan's largest city -- in a bombing blamed on militants during a Shiite religious procession last month, in the worst attack on the city in two years.

Baldia Town mayor Kamran Akhtar said the seven dead were in the rented house at the time of the attack, with no passers-by caught in the blast.

The flattened house was a single storey building with a small courtyard, and an AFP reporter at the scene said the limbs and the head of the victims were visible under the rubble as rescue officials worked to free them.

Mohammad Saleem, a local resident, told AFP he was leaving for his office in the morning when he heard a deafening explosion.

"When I reached the scene, I found the house had already collapsed," he said. "Those people living in this house never got mixed up with their neighbours but nobody took any note of it."

City police chief Ahmad said two people had been arrested at the scene and were being questioned but gave no further details.

Nearly 2,900 people have been killed in attacks in Pakistan since the militant violence intensified in July 2007, with the Taliban increasingly hitting big cities and civilian targets.

Karachi, a cosmopolitan port city far away from the troubled northwest, had largely been spared the bloodshed but there are fears that militants are using the cover of a city of about 14 million people to regroup and plan attacks.

Pakistan's richest city is also plagued by crime and kidnappings, which some analysts say militant groups use to bankroll their insurgency.

Islamists say their campaign, which has become deadlier over the last year, is to avenge military offensives and Pakistan's unpopular alliance with the United States in the eight-war against the Taliban in neighbouring Afghanistan.