Fighting rages in Aleppo amid 'chlorine gas war crime' reports

Fighting continued in the Syrian city of Aleppo on Thursday despite a supposed three-hour ceasefire announced by Russia, two rebel groups and a witness in the city said, as government forces tried to reverse last week's opposition gains.

The fighting rages as the United Nations said it was investigating a evidence of a toxic gas attack on a rebel-held area of the city.

Rebels said the attack - which reportedly left four people dead and many injured - was carried out by government forces using chlorine gas.

The UN special envoy for Syria said a chlorine attack, if confirmed, would amount to a "war crime".

Russia, which backs Syrian President Bashar al-Assad and his government, had annouced a a daily halt to hostilities from 10am until 1pm daily to facilitate the delivery of aid supplies.

However a rebel sources in Aleppo said that the ceasefire had not taken effect. Mohammed Rasheed, spokesman for the rebel Jaish al-Nasr group, said: "No, on the contrary.

"Today since the morning there has been a (government) attempt to advance in the Ramouseh area. There has been a big escalation by Russian warplanes," he added.

A witness in Aleppo near the frontline between the opposition-held eastern sector and the government-held west of the city also reported hearing continued fighting after 10.30am.

A second rebel official said fighting was continuing at 11am local time.

The UN Special Envoy to Syria Staffan de Mistura said on Thursday that the proposed Russian humanitarian daily pause of three hours "is not enough". He said the UN needed at least 48 hours to fix civilian infrastructure that has been damaged during the recent intensification of the fighting.

He also called on both the rebel groups and Syrian government to ease their siege of Aleppo and other towns so the UN can airlift civilians who are in a critical condition.

"Any pause obviously should always be seen and looked at with great interest, because a pause means no fighting, but three hours is not enough," de Mistura told reporters in Geneva. 

Syrian state television reported on Thursday that the army had advanced on Wednesday night under cover of air strikes to positions near the areas that rebels captured last week.

Rasheed of Jaish al-Nasr and Ahmed Hamaher of the Nour al Din al-Zinki group, which is also fighting in Aleppo, said government forces had taken some positions but then been quickly forced back.

Several killed in chlorine attack

Pro-government forces were also accused by medical staff and civil defence workers on Thursday of dropping chlorine gas shells alongside barrel bombs, prompting the UN to launch an investigation.

Photos on the Reuters news agency showed patients breathing through oxygen masks as they received treatment in hospital.

The manager of al-Quds hospital told Reuters that at least four people had died of gas poisoninig and at least 55 were injured with seven still requiring hospital treatment.

French Foreign Minister Jean-Marc Ayrault said he was "concerned by reports of a new chemical attack... that is said to have claimed four lives and left dozens injured."

Washington also expressed concern over the reports, which it said would be in violation of a 2013 UN resolution to dismantle the Syrian government's chemical weapons arsenal.

One pediatrician who signed the letter and spoke to AFP in the eastern districts said he was forced to watch children "die in our arms" because of dwindling medical supplies and repeated bombardment.

On Saturday, rebels broke a three-week government encirclement that had left residents of eastern Aleppo reeling from skyrocketing prices and food shortages.

But the pediatricians, surgeons and other physicians who signed the letter said the situation remained dire.

"Unless a permanent lifeline to Aleppo is opened it will be only a matter of time until we are again surrounded by regime troops, hunger takes hold and hospitals' supplies run completely dry."

The letter accuses Washington of inaction, saying it had seen "no effort on behalf of the United States to lift the siege or even use its influence to push the parties to protect civilians."

"We do not need tears or sympathy or even prayers, we need your action. Prove that you are the friend of Syrians."

Russia plans permanent Syrian air base

Russia is planning to expand its air base in Syria into a permanent military facility, a senior senator said Thursday.

The Hmeimim airbase outside the city of Latakia houses aircraft used in Moscow's bombing campaign in Syria.

"After its legal status is agreed upon, Hmeimim will become a Russian military base. The appropriate infrastructure will be built and our servicemen will live in worthy conditions," Frants Klintsevich, the deputy head of Russia's senate committee for defence, told Izvestia newspaper.

Klintsevich added that the number of Russian jets based in Syria could grow but denied nuclear weapons or heavy bombers could follow.

"Reconnaissance and fire support from the Russian air force allows the Syrian army to successfully complete the tasks at hand," Klintsevich said.

"Russia understands that if measures are not taken, the major terrorist threat will reach it too."

President Vladimir Putin earlier this week told his parliament ratify an agreement signed with Damascus last year to set up the base.