The government fears more institutions will be targeted by bombers
All schools, colleges and universities have been closed across Pakistan a day after suicide bombers attacked a university in the capital, Islamabad.
Eight people died and at least 18 were wounded in the twin blasts at the International Islamic University.
The Taliban said it carried out the attack and there would be more violence unless the army ended its offensive in the tribal areas of South Waziristan.
Meanwhile, a senior al-Qaeda leader was reported killed in North Waziristan.
Abu Musa al-Misri - an Egyptian said to be one of the militants' most senior bomb-makers - was killed in a blast about 10km (six miles) south of the town of Miran Shah, local officials told BBC Urdu.
Reports say two others also died.
It is not clear what caused the explosion. Initial reports that a US drone had struck the house Mr Misri was in proved to be false.
'Sense of loss'
Wednesday's attack in Islamabad was the first since the army launched its offensive against the Taliban in South Waziristan.
International Islamic University students speak about the bomb blast
The eight killed included two suicide bombers.
Following the attack, Pakistan's Interior Minister Rehman Malik said that Pakistan was now in what he called a state of war.
The BBC's M Ilyas Khan, in Islamabad, says the closure of schools and universities in Pakistan is indefinite.
However, they may reopen next week if the security threat decreases, he adds.
A wave of attacks on Pakistani cities has killed more than 180 people during the month of October alone.
In South Waziristan, Pakistani troops are battling to gain control of the key Taliban-held town of Kotkai.
A Taliban spokesman said 40 soldiers had been killed in an attack on a security post near the town. The army acknowledged four dead and said it was meeting fierce resistance.
The army said it had killed 90 militants since beginning its offensive on Saturday, a claim the militants dispute.
Because of reporting restrictions, it is extremely hard to find out what is going on in South Waziristan.
The fighting has caused tens of thousands of civilians to flee the area.