Half of rebel-held Aleppo 'falls to Syrian regime'

Syrian government forces have recaptured half the former rebel stronghold of east Aleppo, a monitor said on Friday, in an offensive that has left bodies in the streets and sparked global outrage.

Rebels put up fierce resistance in the southeastern outskirts of the battered city, but government forces closed in on opposition territory from the east.

President Bashar al-Assad's forces have made swift gains since their offensive against Aleppo - once Syria's commercial powerhouse - began on November 15.

Tens of thousands of civilians have streamed out of the city's east, and Russia has renewed calls for humanitarian corridors so aid can enter and desperate residents can leave.

Regime forces on Friday "consolidated their control" over two eastern districts and were pushing further to squeeze the shrinking rebel enclave, said Syrian Observatory for Human Rights head Rami Abdel Rahman.

"After the recent advances, the regime is comfortably in control of half of former rebel territory in the city's east," he said.

The loss of east Aleppo - a rebel stronghold since 2012 - would be the biggest blow to Syria's opposition in more than five years.

Earlier on Friday, anti-government fighters had successfully rolled back regime gains in Sheikh Saeed on Aleppo's southeastern outskirts.

Sheikh Saeed borders the last remaining parts of Aleppo still in rebel hands - a collection of densely populated residential neighbourhoods where thousands have sought refuge from advancing regime forces.

In preparation for street-by-street fighting in these districts, hundreds of fighters from Syria's elite Republican Guard and Fourth Division arrived in Aleppo Friday, the Britain-based Observatory said.

It said four civilians were killed in rebel rocket fire on government-held areas, bringing to 59 the civilian toll in the city's west.

More than 300 civilians, including dozens of children, have been killed in east Aleppo since the offensive began, according to the Observatory.