Two suicide bombers carried out the attack on War College, interior ministry spokesman Javed Iqbal Cheema said in Islamabad. Security was stepped up across the country, especially at vital military installations, following the attack.

One bomber blew himself up at the gate when the motorcycle was stopped by security personnel, while the other detonated his explosives within the parking lot, triggering several blasts in the CNG tanks of the vehicles parked in the area, city police chief Malik Iqbal said.

Witnesses said they first heard two blasts that occurred almost simultaneously a little after 1 pm. These were followed by two more blasts after a gap of a few minutes.

President Pervez Musharraf, caretaker Prime Minister Mohammedmian Soomro and Pakistan People's Party co-chairman Asif Ali Zardari, whose party is set to form the next government, condemned the attack.