The last rebel-held areas of Aleppo's historic old city have fallen to Syrian government forces, an activist monitoring group says.

The Syrian Observatory for Human Rights said the rebels had withdrawn after army advances during the night. The rebels have held the area around the ancient citadel for the past four years.

The Syrian military now holds more than two-thirds of eastern Aleppo and is seeking to control the whole city. The rebel withdrawal came after days of heavy fighting as government forces moved to split the remains of the rebel-held enclave.

Tens of thousands of civilians are still trapped in the last of the rebel-held districts. The BBC's Lyse Doucet in Aleppo says officials there are preparing for another exodus, as families try to flee under fire in an extremely dire situation.

Food supplies are exhausted and there are no functioning hospitals after months of heavy bombardment. Meanwhile the Russian defence ministry reported that a Russian military adviser in Syria had been killed by rebel artillery fire. Col Ruslan Galitsky died of his wounds after the attack, on a residential area of government-held western Aleppo, it said.

(Source: BBC)