The five remote-controlled bombs were "highly sophisticated" and went off almost simultaneously, Information Minister Shaikh Rashid said on Tuesday.

"This type of device was never used in the country in the past," he said, adding that those who planted the bombs were the "most expert people".

Six people have been questioned over the attack, which caused no injuries, but no arrests have been made, Rashid said.

Foreign ministry spokesman Masud Khan said on Monday that a comprehensive inquiry was under way.

"We will get to the bottom of it, and try to determine who was responsible, what was the motivation," he said.

The government has beefed up security in the country, following the blasts. So far no one has claimed responsibility for the attack.

President blames rebels

Musharraf has blamed the attack on religious hardliners who he said were trying to kill him.

"It was certainly a terrorist act and certainly it was me who was targeted"

Pervez Musharraf,
Pakistani President

"It was certainly a terrorist act and certainly it was me who was targeted," Musharraf, a key ally in the US war on terror, said on national television.

The president had escaped a similar attack in Karachi in April last year when rebels attempted to blow up an explosives-laden van as his motorcade passed by.

Three of the would-be assassins were convicted in October of trying to kill the president and jailed for 10 years.

Musharraf, who seized power in a bloodless coup in October 1999, has infuriated religious hardliners by backing the US-led campaign that ousted the Taliban in neighbouring Afghanistan two years ago.

He has also been criticised for his decision to impose a ceasefire on the Line of Control in divided Kashmir.