Syria conflict

Staffan de Mistura told reporters that he was prepared to personally accompany al-Qaeda-linked jihadists out of the city if it would stop the fighting.

He also appealed to Russia and Syria not to destroy the city for the sake of eliminating militants.

The UN says 275,000 civilians are trapped in the war-torn east of Aleppo.

"The bottom line is, in a maximum of two months... the city of eastern Aleppo at this rate may be totally destroyed," Mr de Mistura told a news conference in Geneva.

The UK-based Syrian Observatory for Human Rights said the blast occurred at the Atmeh crossing, in Idlib province.

Turkey's state-run Anadolu news agency said it took place during a "change of guard" among rebels in the area.

A news agency linked to so-called Islamic State (IS) said a suicide bomber had targeted a rebel convoy.

Turkish-backed rebel factions are currently battling IS militants in another border region further east.

Defence ministry spokesman Igor Konashenkov said the purpose of the system was to guarantee the security of the base from the air.

The move comes amid growing tension with the West. On Monday, the US halted talks with Russia on trying to co-ordinate air strikes against jihadists.

A ceasefire brokered by Washington and Moscow collapsed last month.

"Let me remind you that the S-300 is a purely defensive system and poses no threat to anyone," Maj-Gen Konashenkov said.

"It is unclear why the deployment of the S-300 caused such alarm among our Western partners."

Washington blamed Russia and the Syrian government for intensifying their attacks against civilians.

Last week, the US warned it would halt the talks unless Moscow stops bombing the city of Aleppo.

Russia said it regretted the US move, accusing it of shifting the blame for the collapse of last month's truce.

Aleppo, Syria's largest city in the north, has come under heavy aerial bombardment since the end of the ceasefire two weeks ago.

The extent of the damage was unclear, but videopurportedly of the aftermath showed damaged walls and craters on one side of the M10 hospital.

Three maintenance workers were among those killed, a medical charity said.

Hundreds have died since government forces launched an offensive to take full control of Aleppo two weeks ago.

Her family encouraged her, urging her to open a restaurant and share her culinary prowess.

But in 2011, everything changed. War ripped apart Syria and one day Kassah and her husband were forced to make a tough decision.

"We left Syria because our house was destroyed and there was no school for my children," says the mother of three.

Keeping culture alive

Today, Kassah is back in the kitchen alongside six other Syrian refugees, working for catering service Zeit Zeitoun, olive oil in Arabic.

The Syrian American Medical Society, which supports the hospital, said it had been struck by barrel bombs.

The same facility was hit in a similar attack on Wednesday.

There are also reports of Russian-backed Syrian government forces hitting Aleppo's historic Old City.

And clashes between government troops and rebels on the ground are said to be occurring in several Aleppo neighbourhoods.

Russian and Syrian air forces resumed attacks on the rebel-held east of the city after a partial truce lapsed on 19 September.

In a phone call with Sergei Lavrov, Mr Kerry said the US held Russia responsible for the use of incendiary and bunker bombs against the city.

The US state department said it was making preparations to suspend talks.

Aleppo has come under heavy aerial bombardment since the end of a ceasefire a week ago.

In response to Mr Kerry's phone call, the Russian Deputy Ambassador to the UN, Evgeny Zagaynov, said the "trend" of Russia being blamed for the attacks in Syria must stop.

A spokeswoman said there were only 35 doctors left to care for hundreds of trapped patients, and that the number of casualties was rising.

Medical supplies are also running out, and there is a shortage of blood.

Russian-backed Syrian government forces launched an assault on eastern Aleppo on Thursday after a truce collapsed.

Eastern parts of the city are held by rebels.

Medics in the city are struggling to cope with the huge number of casualties caused by the most sustained and intense aerial bombardment in years.

Supplies of medicine and blood are running low, as a three-week siege by the army begins to have an impact.

An air strike on a pumping station has also left many areas without water.

"The planes are not leaving the skies at all," Brita Hagi Hassan, president of the rebel city council, told Reuters news agency. "Life in the city is paralysed."