The French Ambassador to the United Nations has said that war crimes are currently being committed in the Syrian city of Aleppo.

Speaking at an emergency United Nations meeting on Sunday called to discuss President Bashar al-Assad’s escalating military offensive, Francois Delattre said that the Syrian government is targeting civilians in the northern city, where 250,000 people live under siege conditions.

Rebel-held parts of Aleppo have been under a renewed aerial onslaught by the Syrian and Russian air forces since the Syrian military announced a new campaign to retake the city on Thursday. Ground forces have succeeded in retaking the Palestinian camp of Handarat in the north of Aleppo from rebels, but have been repelled in other areas so far.

At least 200 people have been killed in one of the bloodiest weeks in Syria’s almost six-year-long war, monitors said, but it has been so difficult to document the numbers of wounded and casualties because of the intense bombing that the death toll is expected to rise.

“What’s happening now is annihilation,” Ammar al-Selmo, the head of the local civil defence rescue service, told Reuters this week.

Hospitals are full, so some people are receiving treatment on the floor or in makeshift clinics, doctors said.

More than two million people in both rebel and government held parts of the city are also without water.

Syrians await treatment at a make-shift hospital following air strikes on rebel-held eastern areas of Aleppo (AFP/Getty) (AFP/Getty Images)

“War crimes are being committed here in Aleppo,” Mr Delattre said in his speech to UN delegates in New York. “They must not be unpunished and impunity is simply not an option in Syria.”

The Security Council meeting was called by the UK, US and France to address the unprecedented violence and rapidly deteriorating humanitarian situation in Aleppo.

UN Secretary-General Ban Ki-moon also said that if the offensive was targeting civilians with sophisticated weapons, including incendiary weapons such as napalm, as reported by rebel groups on the ground, it would amount to a war crime.

The situation in Aleppo on 23 September, with regime attacks and territory seen in red, rebels in green, Kurds in yellow and Isis in black (Liveuamap)

The UN’s envoy to Syria Staffan de Mistura expressed fears that the regime’s announced ground offensive will be a “slow, grinding, street by street fight, over the course of months if not years.”

Several ambassadors attacked Russia’s actions in supporting the Syrian government. Russian representative Vitaly Churkin said that terrorists inside East Aleppo were to blame for using women and children as shields, and that every effort was taken to minimise harm to civilians caused by air strikes.

All diplomatic peace-building efforts between Syria and Russia and the international community have now totally collapsed.

Aleppo residents plead for help as Syria fighting rages

The renewed attack on Aleppo and Russia’s apparent decision to abandon the latest efforts to reinstall last week’s ceasefire appear to signal that the Syrian regime is more determined than ever to crush all opposition in the country.

If Assad’s forces succeed in retaking Aleppo, there will only be pockets of rebels left in sparsely populated areas in the far north and south of Syria. Isis still holds on to vast swathes of north-east Syria and Iraq and several Islamist groups are operating in the country. Kurdish militias have declared autonomy for themselves in the north of the country.

The main rebel umbrella group said in a statement on Sunday they could not accept Russia as a sponsor of any new peace initiative “because it was a partner with the regime in its crimes against our people”.

Assad’s fortunes improved a year ago when Russia began providing military as well as financial assistance.

The president vowed to retake the entire country from terrorists on the eve of last week’s ceasefire.