Syria's regime said Thursday it was ready to take part in new talks in Geneva aimed at ending the war but appeared to make its participation conditional on which opposition groups will attend.

It came as the Islamic State (IS) jihadist group pushed further into a key city in eastern Syria in fighting that left more than two dozen regime loyalists reported dead.

Amnesty International said on Wednesday that nearly three months of Russian air raids in Syria have killed hundreds of civilians, many in targeted strikes that could constitute war crimes.

Some strikes "appear to have directly attacked civilians or civilian objects by striking residential areas with no evident military target and even medical facilities, resulting in deaths and injuries to civilians," Amnesty Middle East and North Africa director Philip Luther said in a statement.

Syrian activists have accused regime forces of using a "toxic gas" during clashes in a flashpoint town southwest of Damascus, saying five men were killed.

A local activist group in Moadamiyet al-Sham, where hundreds died in August 2013 in chemical strikes, accused President Bashar Assad's troops of firing a toxic chemical at the town on Tuesday.

The father of toddler Aylan Kurdi, whose lifeless body on a Turkish beach became a symbol of the refugee crisis, has made a Christmas appeal to the world to open its doors to Syrians fleeing conflict.

The message, to be broadcast by Britain's Channel 4 on Christmas Day, comes after the U.N. refugee agency said that more than one million migrants and refugees reached Europe this year.

The U.N. Security Council Tuesday renewed a resolution facilitating the cross-border delivery of aid to millions of Syrians, while complaining previous such measures were not seen through on the ground.

The text was adopted unanimously by the 15 member states, which include Syrian ally Russia.

The Islamic State group is using some stores in Lebanon as a front for its smuggling of Syrian artifacts, reported An Nahar daily on Wednesday.

It revealed that a recently arrested IS member had confessed to being related to the owner of a butcher shop in the northern city of Tripoli and that the meat shipments received from Syria are not limited to the products he sells in his shop.

Syrian President Bashar Assad, in one of his rare public appearances, attended the Muslim celebration of Mawlid marking the Prophet Mohammed's birthday in a Damascus mosque Tuesday, state media reported.

The ceremony, broadcast on state television, was held in al-Akram mosque in the capital's western district of Mazzeh.

The Syrian Observatory for Human Rights said Tuesday that Russian air strikes have killed 2,132 people in Syria, a third of them civilians, since they began on September 30.

Of those killed, 598 were fighters from the Islamic State group and another 824 from al-Nusra Front, the Syrian affiliate of al-Qaida, and other rebel groups.

Islamic State group jihadists killed nine Syrian students when they shelled a school in the eastern city of Deir Ezzor on Tuesday, state news agency SANA reported.

The Syrian Observatory for Human Rights said nine girls were killed and another 20 wounded, mostly students from the regime-held district of Hrabesh.

The next round of talks aimed at easing the violence in war-torn Syria will be held at the U.N.'s European headquarters in Geneva early next year, a U.N. spokesman said Tuesday.

"The talks will take place in Geneva, but we don't have the exact date," U.N. spokesman Rheal LeBlanc told AFP.