* Rebels attack to take back area seized by government
* Planes bomb camp, residential areas
* UN security council to discuss escalation in fighting
* Scores killed in most fierce attack on Aleppo yet

Warplanes bombed a strategic camp on the northern edge of Aleppo on Sunday as Syrian government and rebel forces battled for control of the city in a Russian-backed offensive that appears to have buried any hope for diplomacy.

The United Nations Security Council will meet at 11 a.m. (1500 GMT) to discuss the sharp escalation in violence since a ceasefire collapsed last week. But the rebels said any peace process would be futile unless ‘scorched earth bombing’ by Russian-backed government forces stopped immediately.

Capturing the rebel-held half of Syria's largest city, where more than 250,000 civilians are trapped, would be the biggest victory of the civil war for President Bashar al-Assad's forces.

They have achieved their strongest position in years thanks to Russian and Iranian support and launched a fresh offensive for a decisive battlefield victory on Thursday. In the first major advance, they seized control of the Handarat Palestinian refugee camp, north of Aleppo.

Rebels counter attacked and said on Sunday they had retaken the camp before the bombing started.

‘We retook the camp, but the regime burnt it with phosphorous bombs,’ said Abu al-Hassanien, a commander in a rebel operations room that includes the main brigades fighting to repel the army assault.

The army, which is being helped by Iranian-backed militias, Lebanon's Shia Hezbollah militant group and a Palestinian militia, acknowledged rebels had retaken Handarat.

‘The Syrian army is targeting the armed groups' positions in Handarat camp,’ a military source was quoted on state media as saying.

Planes also continued to pound residential areas on Sunday, flattening buildings, rebels and residents said. They say air strikes have intensified, with more powerful weapons, since the new offensive began.

‘The Assad regime and with direct participation of its ally Russia and Iranian militias has escalated its criminal and vicious attack on our people in Aleppo employing a scorched earth policy to destroy the city and uproot its people,’ a statement signed by 30 mainstream rebel groups said on Sunday.

The Syrian Observatory for Human Rights, a monitoring group, said at least 45 people, among them 10 children, were killed in eastern Aleppo on Saturday.

The army says it is targeting only militants.

Hundreds of thousands of people have been killed in the civil war and 11 million driven from their homes.

DIPLOMATIC EFFORTS

Russia and the United States agreed on Sept. 9 a deal to put the peace process back on track. It included a nationwide truce and improved humanitarian aid access but it collapsed when an aid convoy was bombed killing some 20 people.

US Secretary of State John Kerry, who hammered out the truce in months of intensive diplomacy, pleaded with Russia to halt air strikes.

In a meeting on Saturday in Boston, Kerry and his counterparts from the EU, Britain, Germany, Italy and France said Russia should ‘take extraordinary steps to restore the credibility of our efforts, including by halting the indiscriminate bombing by the Syrian regime of its own people.’

British Foreign Secretary Boris Johnson said Russia was guilty of prolonging the war in Syria and may have committed war crimes by targeting an aid convoy.

‘When it comes to instances such as the bombing of aid targets in Aleppo, we should be looking at whether or not that targeting is done in the knowledge that those are wholly innocent civilian targets, that is a war crime,’ he said in a BBC interview aired on Sunday.

Sunday's United Nations meeting, which will be public, was requested by the United States, Britain and France.

The rebels said in their statement they could not accept Russia, a member of the UN Security Council, as a sponsor of a new peace initiative ‘because it was a partner with the regime in its crimes against our people.’

It said Russian-backed Syrian forces were using napalm and chemical weapons without censure from the international community.

UN investigators are looking into the alleged use of the incendiary weapons phosphorus and napalm in several cities.

The war has ground on for nearly six years, drawing in world powers and regional states. Islamic State - the enemy of every other party to the conflict - has seized swathes of Syria and neighbouring Iraq. All diplomatic efforts have collapsed.

World powers appeared to believe that neither Assad nor his opponents were capable of decisive victory on the battlefield.

But Russia's apparent decision to abandon the latest peace process could signal it now thinks that victory is in reach, at least in the western cities where the majority of Syrians live.

Assad's fortunes improved a year ago when Russia joined the war on his side. Since then, Washington has worked hard to negotiate peace with Moscow, producing two ceasefires. But both proved short-lived, with Assad showing no sign of compromise.

Moscow says Washington failed to live up to its side of the latest deal by separating mainstream insurgents from hardened jihadists.

FIERCE BATTLES

Outside Aleppo, anti-Assad fighters have been driven mostly into rural areas. Nevertheless, they remain a potent fighting force, which they demonstrated with an advance of their own on Saturday.

The Syrian Observatory for Human Rights said on Saturday rebels, including the jihadist Jund al-Aqsa group, had seized two villages in northern Hama province, an area that is close to the coastal heartland of Assad's Alawite minority sect.

A Syrian military source said the army was ‘fighting fierce battles’ around the two villages, Maan and al-Kabariya.

Damascus and its allies including Shia militia from Iran, Iraq and Lebanon have encircled rebel-held areas of Aleppo gradually this year, achieving their long-held objective of fully besieging the area this summer with Russian air support.

A pro-government Iraqi militia commander in the Aleppo area told Reuters the aim was to capture all of Aleppo within a week.

A Western diplomat said on Friday the only way for the government to take the area quickly would be to totally destroy it in ‘such a monstrous atrocity that it would resonate for generations’.