Syrian rebels and government forces have clashed in southern Aleppo, including during the period of a promised Russian lull to allow humanitarian convoys in, according to media reports.
Lorries carrying food were unable to enter Aleppo on Thursday because of intense bombardment, the AFP news agency reported from the rebel-held east of the city where private vendors managed to deliver fresh produce.
Syrian state news agency said army troops seized territory south of Aleppo on Thursday, adding that rebel fire killed four civilians in a government-held district. But it made no mention of the "humanitarian windows" announced by Russia.
|Lorries carrying food were reportedly unable to enter Aleppo on Thursday because of intense bombardment [Abdalrhman Ismail/Reuters]
Human Rights Watch said on Thursday it had documented six strikes by regime or Russian warplanes on health facilities in the north that killed 17 people in the past two weeks.
"With heavy bombing continuing relentlessly in Aleppo especially, hospitals and clinics need to be treated as the sacred life-saving places they are, not as additional bombing targets," said deputy Middle East director Nadim Houry.
French Foreign Minister Jean-Marc Ayrault said in a statement on Thursday that he was "concerned by reports of a new chemical attack... that is said to have claimed four lives people and left dozens injured."
Activists accused government forces on Wednesday of carrying out an attack using chlorine gas on a rebel-held residential neighbourhood in Aleppo.
READ MORE: Why Aleppo matters
Fifteen of the only remaining doctors in the eastern half implored US President Barack Obama on Thursday to protect civilians from atrocities in their city.
"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 said.
"We do not need tears or sympathy or even prayers, we need your action. Prove that you are the friend of Syrians," they wrote.
An estimated 1.5 million people live in Aleppo, including about 250,000 in rebel-held districts.
Battle for Raqqa
Further east, Russian raids hit Raqqa, the stronghold of Islamic State of Iraq and the Levant (ISIL, also known as ISIS), killing at least 24 civilians and wounding 70 people, said the Observatory.
The monitor said another six people were also killed but it had not yet confirmed how many of them were civilians or ISIL fighters.
Russia said the raids destroyed a "chemical weapons factory" on Raqqa's outskirts as well as a weapons storage facility and ISIL training camp to the north and southeast.
Its defence ministry said ISIL suffered "significant material damages" in the strikes and that "a large number of fighters have been killed".