Syrian army soldiers loyal to President Bashar al-Assad walk on Hilan Hill, as smoke rises in the background from a village they claim to be shelling. Picture: George Ourfalian

Aleppo - Syria's army broke a year-long siege of Aleppo central prison on Thursday, cutting off a major rebel supply route, reports said, less than a fortnight before President Bashar al-Assad's expected re-election.

Tanks and armoured vehicles rolled into the grounds of the prison in the main northern city and intense celebratory gunfire was heard inside the sprawling complex, the Syrian Observatory for Human Rights said.

The breakthrough came hours before a UN Security Council vote on a resolution to give the International Criminal Court jurisdiction over alleged war crimes in Syria, which Russia has threatened to veto.

It puts the army and its allies, including Lebanon's Hezbollah, within reach of Castelo road, which rebels in Aleppo city have relied on as a supply route leading to the countryside as a rear base.

The province of Aleppo borders Turkey, a key supporter of Syria's revolt and home to hundreds of thousands of refugees that have fled the three-year conflict estimated to have killed more than 160 000 people.

“After a siege of nearly 13 months by Al-Nusra Front and Islamist rebels, regular armed forces backed by pro-regime fighters were able to break the siege of Aleppo central prison,” the Observatory said.

The army's advance in the area around the prison in the north of Aleppo, Syria's second city, was preceded by aerial assault on Thursday using highly destructive shrapnel-packed barrel bombs, it added.

Fighting in the area has killed at least 50 rebels and an unspecified number of pro-regime fighters since Tuesday, according to the Britain-based group that relies on sources on the ground for its reports.

Rebel fighters have repeatedly attacked the prison since April 2013, hoping to free the approximately 3 500 detainees inside, who are reportedly being held in dire conditions.

Government soldiers inside the prison have fought to defend the complex.

In early February, a group of rebels launched a major assault on the prison and took control of the vast complex, before being partially driven back by air raids.

Many prisoners died during the siege because of a lack of food and medicines, and poor hygiene.

The prison had nearly 4 000 prisoners before the siege, including Islamists. Poor humanitarian conditions and the bombardment of the area have caused the death of about 600 inmates, according to the Observatory.

Its capture comes on the heels of another significant victory for the Assad regime, which this month reclaimed the Old City of Homs, Syria's third city once dubbed the “capital of the revolution”.

The conflict flared when Assad's opponents took up arms in response to a bloody crackdown on a popular uprising that erupted in March 2011. It is estimated to have claimed at least 162 000 lives and displaced nearly half the country's population.

Despite the civil war, the Damascus regime is to stage a presidential election on June 3 in the areas under its control.

The exiled opposition has dismissed the election as a “farce”, while the United States has branded it a “parody of democracy”.

However, Assad, running for a third seven-year term against two virtual unknowns, is expected to stroll to victory in the poll.

Meanwhile, Russia has said it will use its veto to block a French-drafted resolution before the UN Security Council on Thursday that calls for the International Criminal Court to be given jurisdiction over alleged war crimes in Syria.

Moscow's ambassador to the UN, Vitaly Churkin, dismissed the initiative as a “publicity stunt” and said it would undermine efforts to find a political solution.

It would be the fourth time that Moscow, the Assad regime's most powerful ally, has used its veto to block Western resolutions since the start of the conflict. - AFP