Russian strikes slow rebel assault in Syria's Aleppo

The assault began on Sunday and is intended to ease the encirclement of the opposition-held east of Aleppo city, where an estimated 250,000 residents have been under a regime siege since July 17.

The British-based Syrian Observatory for Human Rights described it as the largest rebel attack in Aleppo since 2012, when fighting reached the city and left it roughly divided between the opposition control in the east and regime forces in the west.

But government troops backed by Russia's air force have put up a fierce defence, the monitor said.

"The Russian raids didn't stop all night on the front lines" there, said Observatory head Rami Abdel Rahman.

"This has slowed the offensive and allowed regime troops to retake five of the eight positions that rebels had taken since Sunday," he added.

The strikes came despite an appeal by US Secretary of State John Kerry on Monday for Russia to "restrain" itself and its ally in Damascus.

"It is critical, obviously, that Russia restrain both itself and the Assad regime from conducting offensive operations, just as it is our responsibility to get the opposition to refrain from engaging in those operations," he told journalists.

Kerry said regime attacks had prevented the warring parties from meeting for negotiations on Monday, the target date set for the regime and opposition forces to agree on the framework of a political transition.

- 'Last chance for rebels' -The offensive groups fighters from Fateh al-Sham Front, formerly Al-Qaeda affiliate Al-Nusra Front, as well as the powerful Islamist Ahrar al-Sham and other factions.

The Observatory said 50 rebels and allied jihadists had been killed since the operation began on Sunday, as well as dozens of regime troops.

Its main target is the government-held district of Ramussa, on the southwest outskirts of Aleppo.

The route used by regime forces and civilians living in government-controlled parts of Aleppo runs through Ramussa. Its capture would both cut off government forces and open a new route into the city for rebels.

The Observatory said at least 30 civilians had also been killed since Sunday in opposition bombardment of government-held southwestern districts of Aleppo.

According to a Syrian military source, around 5,000 pro-regime fighters, including Iranian forces and the powerful Lebanese Shiite movement Hezbollah, are taking part in the battle for the city, including fighting north of Aleppo.

Facing off against them are thousands of fighters from the Fateh al-Sham Front and allied groups, according to the Observatory.

"This battle is the last chance for rebels. If they lose, it will be difficult for them to launch a new assault to break the siege," Abdel Rahman said.

"For the regime also, it's a question of life or death. They've been preparing for this battle for months and it'll be a tough blow for its troops if they lose," he added.

- Russian helicopter shot down -Residents in east Aleppo have reported food shortages and rising prices since government troops seized the last remaining road into opposition-held districts on July 17.

Last week Russia announced the opening of "humanitarian corridors" to allow residents and surrendering fighters to flee the east for government-held territory.

The announcement was met with scepticism by both residents and some in the international community, but Damascus and Moscow say some residents and fighters have begun using the passages.

On Tuesday, Syrian state media said "dozens of families" had crossed from the east, after reporting similar crossings over the weekend.

Residents and rebels on the ground had dismissed the reported weekend crossings as "lies."

Syria's conflict has killed more than 280,000 people and drawn in world powers on both sides since it erupted in March 2011.

Russia began an aerial campaign in support of Damascus last September, and has lost 18 forces since its intervention began.

The latest deaths came Monday, when Moscow announced five people on board a military helicopter were killed when it was shot down over Idlib province.

It was the single deadliest incident for Russia since its intervention began.

There was no immediate claim of responsibility for the incident, which occurred in an area controlled by a rebel alliance dominated by the Fateh al-Sham Front.

ram/sah/mjg/dr

© 1994-2016 Agence France-Presse