°®Âþµº

At least 39 people were killed after a Russian air raids on a prison complex on Saturday, run by al-Qaeda's Syrian affiliate in the country's northwest, a monitor said.

The Syrian Observatory for Human Rights said the strikes hit a al-Nusra Front building, which lies close to a popular market in Maarat al-Numan in Idlib province.

The building housed the group's religious court and a jail.

Activists reported massive damage to the courthouse and said dozens of people had been killed or maimed in the attack.

A video showed rescue workers attempting to reach civilians trapped under rubble.

Observatory head Rami Abdel Rahman said the dead included prisoners and Nusra fighters, and could include civilians who had been at the market.

Dozens of people were also wounded and many remained trapped under the rubble, the monitor said.

Russian warplanes have been conducting air strikes in Syria since 30 September against the Islamic State group and "other terrorist groups". The vast majority of air raids have hit rebel areas rather than IS.

In December Amnesty International said Russian airstrikes in Syria that have killed hundreds of civilians and cause massive destruction may amount to war crimes.

Russian airstrikes on seven residential areas in the Syrian city of Idlib have killed at least 47 people in December.

Although Nusra and IS are both extremist organisations, they are fierce rivals and regularly clash in Syria.

The Britain-based Observatory has an extensive network of sources inside Syria and identifies casualties by the type of aircraft flown and the munitions used.

Idlib province is controlled by the Jaish al-Fatah rebel alliance, headed by Nusra and Islamist group Ahrar al-Sham.

Syria's conflict first erupted with anti-government demonstrations in March 2011 but has since morphed into a bloody war that has left more than 260,000 people dead.