An intense battle for control of Palmyra in Syria has reportedly been swinging back and forth between government forces and ISIL fighters.

Moscow said its airstrikes had helped force the hardline Islamists out of the ancient city overnight. The Russian Defence Ministry its jets carried out 64 sorties during the operation, killing more than 300 militants.

However, a news agency linked to so called Islamic State claims the militants are now back in control of Palmyra after briefly retreating. That account was backed up by the British-based Syrian Observatory for Human Rights, which monitors the conflict.

ISIL launched a surprise offensive on the UNESCO world heritage site last week seizing nearby oil and gas fields.

The Syrian army is believed to have sent reinforcements to Palmyra which ISIL first took in May 2015 until they were eventually kicked out in March this year.