Syrian government war planes have bombed opposition-held areas of Syria and President Bashar al-Assad's forces and rebels fought on the outskirts of the capital.

The air force pounded Damascus's eastern suburbs and rebel-held areas of Aleppo, the second city and commercial capital, as well as several rural towns and villages.

Residents of the capital began the new year to the boom of artillery hitting southern and eastern outskirts, which form a rebel-held arc around the capital.

The heart of the city is still firmly under government control.

In the city centre, soldiers manning checkpoints fired celebratory gunfire at midnight although the streets were largely deserted.

An estimated 45,000 people have been killed in the conflict, which started in early 2011 with peaceful protests demanding democratic reforms.

A resident of the central city of Homs said artillery shelling had hit its Old City.

Homs lies on the north-south highway and parts of the ancient city have been levelled during months of clashes.

Government forces ousted rebels from Homs early last year but militants have slowly crept back in.

The opposition-linked Syrian Observatory for Human Rights, a British-based monitoring group, reported 160 people killed on the final day of 2012, including at least 37 government troops.

The group's reports cannot be verified.

President Assad's forces now rely more on air strikes and artillery bombardment rather than infantry.

Residential areas where rebels are based have been targeted, killing many civilians.

Rebels have taken swathes of the northern mountains and eastern desert but have struggled to hold cities, saying they are defenceless against Mr Assad's Soviet-equipped air force.

The civil war in Syria has become the longest and deadliest of the conflicts that rose out of the uprisings that swept through the Arab world over the past two years.

Many Sunni Muslims, the majority in Syria, back the rebellion, while Mr Assad, who hails from the Shia-derived Alawite minority sect, is backed by some minorities who fear revenge if he falls.

His family has ruled Syria harshly since his father seized power in a coup 42 years ago.

A year ago, many diplomats and analysts predicted Mr Assad would leave power in 2012.

But he has proved resilient, none of his inner circle have defected and he still largely retains control of his armed forces.

Diplomatic efforts to end the war have faltered, with the rebels refusing to negotiate unless Mr Assad leaves power and him pledging to fight until death.

Most Western and Arab states have called for him to leave power. He is supported by Russia and Shia Iran.

In the final days of 2012, international mediator Lakhdar Brahimi called on countries to push the sides to talk, saying Syria faced a choice of "hell or the political process".