BEIRUT  - At least 35 people, including children, were killed as Syrian forces backed by combat helicopters battled rebels in a new front in and around east Damascus on Monday, a monitoring group said.

Rebels from the Free Syrian Army claimed to have downed a military helicopter in the district of Qaboon during heavy shelling and fierce fighting that also engulfed nearby Jubar as well as several towns outside the capital. In the single deadliest incident, 12 people including children died in shelling in the town of Zamalka, according to the Syrian Observatory for Human Rights. The Observatory reports and the authenticity of the video could not be verified because of the severe restrictions on media operating in Syria.

“Effectively the army is going from west to east around Damascus, while we are trying to get back into the city, this time in a more organised way,” a rebel commander who identified himself only as Selim told AFP.

The increasing brutal conflict, which had been largely concentrated in the provinces, first hit Damascus with a vengeance last month when fierce battles erupted across the southern belt of the capital.

Troops then launched a major offensive on districts seized by rebels, claiming to have the city back under its control on Aug 4.

Rebels have since used hit-and-run tactics in the capital, waging what analysts have described as urban guerrilla warfare against the militarily superior but thinly stretched army.

Selim said that after launching a major offensive on the southwestern belt last week, including a “massacre” in the town of Daraya, the army’s new focus was the Ghuta area in the countryside east of Damascus.

In what would be another coup for anti-regime fighters, an FSA brigade claimed it had shot down an army helicopter in Damascus, two weeks after rebels said they had downed a warplane in the eastern province of Deir Ezzor.

“It was in revenge for the Daraya massacre,” a spokesman for the rebel Badr Battalion, Omar al-Qabooni, told AFP via Skype. He said the rebels had found the body of the pilot after the chopper plummeted to the ground in a ball of flames. The claims could not be independently verified.

State television said only that a helicopter crashed near a mosque in Qaboon without giving the cause. Rebels also attacked several army checkpoints, and killed at least six soldiers in a bomb attack on a military vehicle in the Ghuta area, the Observatory said.

The escalation in east Damascus comes after the Observatory said at least 334 people were killed in a ferocious five-day onslaught of shelling, summary executions and door-to-door raids in Daraya in the southwest.

In Syria’s other key battleground in the north, regime forces pounded the Izaa district of the main city of Aleppo, the Observatory said, reporting a nationwide toll on Monday of 59.

The army was also bombarding several besieged districts of the central city of Homs, which has faced near constant shelling for more than two months, the Observatory said.

A former Lebanese minister confessed to plotting sectarian killings along with Syria’s security chief, according to alleged leaked security documents published by a local newspaper.

Former information minister Michel Samaha, who has close links to the Damascus regime, was charged earlier this month by Lebanon’s chief military prosecutor with planning attacks in Lebanon and of transporting explosives. Al-Joumhouria newspaper on Monday published a picture of Samaha allegedly giving a bag stuffed with cash to an undercover agent at his Beirut home, along with 10 pages of documents alleged to be records of the investigation.

“I put the bombs in my car while I was at Mamluk’s office in Damascus,” Samaha was quoted as saying in the documents, referring to feared Syrian security chief Ali Mamluk.

UN leader Ban Ki-moon was “shocked” by the reports of a new massacre in Syria and demands an independent inquiry, his spokesman said Monday.

Reports of hundreds of bodies found in Daraya near Damascus on Sunday after raids by government troops highlighted the lack of protection for civilians in the Syria conflict, said Ban’s spokesman Martin Nesirky.

“The secretary general is certainly shocked by those reports and he strongly condemns this appalling and brutal crime,” Nesirky told reporters. “Where hundreds of civilians have been killed in Daraya, this needs to be investigated immediately in an independent and impartial fashion,” the spokesman added.

French President Francois Hollande warned Monday that the use of chemical weapons by the Syrian regime would be a legitimate reason for a foreign intervention. “We with our allies remain very watchful to prevent the use of chemical weapons by the regime, which would be for the international community a legitimate cause for direct intervention,” Hollande said in a speech to French diplomats.

Hollande also said France was ready to recognise a provisional Syrian government once it was formed and urged rebels to establish one as soon as possible. Hollande also said the opposition of Russia and China to action against the Syrian regime was weakening the United Nations. “I am saying to Russia and to China that their attitude in the Syria crisis is weakening our capacity to fulfil the mandate given us by the United Nations charter,” he said.