Two suicide bombings at an Islamic university in the Pakistani capital of Islamabad killed four people and injured 18, police say.

A police officer said blasts at the International Islamic University on Tuesday took place in a women's cafeteria and a faculty building.

The attacks followed warnings this week by authorities that militants might strike at schools and universities. The warnings had led many schools to close.

Police superintendent Abdul Ghafar Quaiserani said the two suicide bombers struck at approximately the same time. Both of the attackers died in the blasts.

No group has claimed responsibility for the attack.

The university attracts students from around the world. The campus on the outskirts of Islamabad has roughly 18,000 students. The school is a hub of Islamic learning, but students also study secular topics, including management and computer science.

Students stone minister's motorcade

Pakistan has been hit by several attacks from Islamic militants in recent weeks. Officials had been expecting more attacks after the Pakistani army launched an offensive against al-Qaeda and Taliban strongholds in the semi-autonomous region of South Waziristan. Roughly 30,000 soldiers are engaged with about 10,000 militants.

"It seems that [militant] sympathizers or collaborators are doing this to divert attention from the military operation," university president Dr. Anwar Hussain Siddiqui said following the attacks at the school. "They are trying to create panic in the capital city."

"Those who call themselves champions of Islam, they have today proved by attacking the Islamic university that they are neither friends of Islam nor Pakistan," Rehman Malik, the country's interior minister, said at the university. Angry students later pelted Malik's motorcade with stones as he left the campus.

Some students at the university refused to believe that militants were behind the attack.

"It shows clearly that anti-Islamic elements are involved in these attacks," said economics student Abul Hassan.

With files from The Associated Press