Suicide bombers driving vehicles packed with explosives blew themselves up near security targets in northern Syria on Wednesday, killing at least 22 people, state-run media and activists said.

The near simultaneous attacks in the city of Idlib brought the carnage of Syria's civil war to a second major urban centre in the country's north in as many days, following the massive blasts a day earlier that killed 87 people at a university in the commercial hub of Aleppo.

There were conflicting reports about the number of explosions Wednesday in Idlib, where rebels fighting to topple President Bashar al-Assad control much of the countryside, while the regime remains in charge of the city itself.

The state-run SANA news agency said two suicide bombers hit a pair of roundabouts in the city, killing 22 people and wounding 30.

Syrians gather at the scene of the explosion outside Aleppo University, which killed more than 80 people and injured more than 150. (AFP/Getty Images)

It said security forces foiled two other would-be suicide bombers in the surrounding countryside who were allegedly planning to target security forces and civilians.

A Syrian government official, however, said three bombings struck a major highway and a roundabout in Idlib city Wednesday, killing 22 people.

The Britain-based Syrian Observatory for Human Rights also reported triple car bombings, but said they targeted security vehicles near the local security headquarters and a checkpoint. At least 24 people were killed, most of them regime forces, it said.

The conflicting reports could not immediately be reconciled.

No claim of responsibility

There was no immediate claim of responsibility for Wednesday's bombings, but Jabhat al-Nusra, an al-Qaeda affiliated group, has claimed responsibility for suicide blasts and other attacks on Syrian government targets in the past.

A Syrian rebel looks at houses destroyed by the Syrian Air force in a suburb of Damascus. (Goran Tomasevic/Reuters)

The Obama administration has labelled the group a terrorist organization.

The bombings in Idlib follow the massive blasts Tuesday that rocked Aleppo University, setting cars alight and blowing the walls off dormitory rooms. It remains unclear what caused the explosions, which hit the campus as students took exams.

The Observatory said 87 people were killed and warned that the death toll could rise even further because medics have collected unidentified body parts and some of the more than 150 wounded are in critical condition.

Syria's Ministry of Higher Education suspended classes and exams at all Syrian universities on Wednesday, "in mourning for the souls of the heroic martyrs who were assassinated by the treacherous terrorist hand," the state news service reported.

The SANA report quoted the minister of higher education, Mahmoud Mualla, as saying that Assad had ordered the reconstruction of Aleppo University "with the utmost speed."

The opposition and the government have blamed each other for the university blasts, which marked a major escalation in the struggle for control of Aleppo — Syria's largest city and once the country's main commercial hub.

Activists said forces loyal to President Bashar al-Assad launched two airstrikes on the area at the time of the blasts, while Syrian state media said a "terrorist group" — the government's shorthand for rebels — hit it with two rockets.

The scale of destruction appeared inconsistent with the rockets the rebels are known to possess.

Confirmation of events in Syria difficult

The competing narratives about what caused the blasts highlighted the difficulty of confirming reports from inside Syria.

A Syrian rebel runs for cover in a Damascus suburb Wednesday. (Goran Tomasevic/Reuters)

The Syrian government bars most media from working in the country, making independent confirmation of events difficult. Both anti-regime activists and the government sift the information they give to journalists to boost their cause. And civilians stuck in the middle avoid talking to the media, fearing reprisals from both sides for speaking their minds.

Aleppo has been the focus of a violent struggle for control since rebel forces, mostly from rural areas north of the city, pushed in and began clashing with government troops last summer.

The university is in the city's west, a sector still controlled by the government. Both activists and the Assad regime said those killed in Tuesday's blasts were mostly students taking their mid-year exams and civilians who sought refuge in the university dorms after fleeing violence elsewhere.

On Tuesday, Syria's UN Ambassador, Bashar Ja'afari, told a Security Council meeting on combatting terrorism that "a cowardly terrorist act targeted the students of Aleppo University" as they sat for their mid-terms. He said 82 students were killed and 152 were wounded.

Syria's crisis began with political protests in March 2011 but quickly descended into a full-blown civil war, with scores of rebel groups across the country fighting Assad's forces. The UN said this month that more than 60,000 people have been killed in the violence.