Russian Foreign Minister Sergei Lavrov met for talks on Syria with his Syrian and Iranian counterparts in Moscow. The trilateral meeting took place as the Syrian army's siege of the rebel-held districts of the city of Aleppo continued.

A trilateral talk in a format the Russian host called "effective".

"We stressed first of all the need for the continuation and intensification of the fight against the terrorists, as well as the parallel improvement of the humanitarian situation, the ceasefire regime and, of course, the urgent launch of the inter-Syrian negotiations in accordance with the UN decisions, without any preliminary terms," said Sergei Lavrov.

Western powers are considering new sanctions to pressure both Russia and Syria into halting their offensive against rebel-held parts of Aleppo, which had drawn international outrage.

Syrian Foreign Minister says that "fighting terrorism and liberating Aleppo from terrorists" is crucial and will not be curtailed by what he described as "the conspiracy against Syria for more than five years under the guidance of the US." He added that recent so-called "humanitarian pause" in the Aleppo fighting was ruined by fighters, whom he called terrorists, firing on the evacuation corridors.

"We are ready to again repeat this attempt after we receive guarantees that confirm that the countries supporting these terrorist organisations are prepared to act so that civilians could use the cease-fire (to leave the city)." said Syrian Foreign Minister Walid Al-Moallem.

Moallem said during meetings with his Iranian counterpart he was sure they would form "constructive decisions" .

"The principles that dominate our opinions on Syria are respect for sovereignty, territorial integrity and the political independence of the Syrian government. It is also important to recognise the voice of the Syrian nation itself and let them determine their own destiny," said Iranian Foreign Minister Mohammad Javad Zarif.

Iran and Russia are key financial and military supporters of President Bashar al-Assad's regime.

The Moscow talks took place as rebels launched a large-scale offensive to break the government's siege of Aleppo's opposition-held eastern districts, while also targeting the government-controlled western districts.