BENGHAZI, Libya (AFP) - Militants claiming affiliation with the Islamic State in Iraq and Syria (ISIS) group took over the university in the Libyan city of Sirte Thursday, leading it to suspend classes and postpone exams, a professor said.

The incident came a day after dozens of gunmen paraded through the streets of the Mediterranean coastal city, 450km east of Tripoli, in a convoy, witnesses said.

It also came as Fajr Libya (Libya Dawn), a coalition of militias that controls Libya's capital and much of the lawless country's west, said it had sent units to "restore security in the city."

Social media showed photos of hooded gunmen in pick-up trucks and 4x4 vehicles mounted with anti-aircraft guns, brandishing the black flag of ISIS, which has seized large swathes of Syria and Iraq and is believed to have extended its presence to the North African country.

Witnesses said the gunmen had also taken over the once grandiose Ouagadougou Centre in what is the hometown of the late Muammar Gaddafi, where the then dictator once organised extravagant African or Arab summits.

An AFP photographer who managed to visit the city briefly, said the Fajr Libya and ISIS forces were keeping their distance from each other and that there had been no hostilities between them.

Last week, militants seized state-run Radio Sirte and several government buildings in the city, hometown of Muammar Gaddafi, which has become a bastion of Islamic extremism since the dictator's overthrow and death in 2011.

Sirte is a bastion of a group called Ansar al-Sharia, classified as a terrorist organisation by the United Nations, which is believed to have links to ISIS.

Several days ago, ISIS affiliates in Libya released a video showing their beheading of 21 Coptic Christians, most of whom were Egyptian, taken prisoner in the country. That prompted Egypt to bomb militant targets in Libya and to threaten further action.