The Syrian government has extended its intense aerial campaign against rebel-held areas of the northern city of Aleppo, conducting a series of raids and killing at least 26 people, according to a monitoring group.

The Syrian Observatory for Human Rights said on Monday that 12 men, 11 children and three women were killed when Syrian army helicopters dropped weapons on neighbourhoods in the east of Aleppo.

Rebel-held areas of the city have been subjected to a punishing string of barrel bomb attacks by Syria's army in the past three days, with at least 36 people killed on Sunday and 85 killed on Saturday, according to the NGO.

The Syrian Observatory said January was the bloodiest month in the conflict so far, with 5,794 deaths recorded.

Al Jazeera cannot independently confirm the claims because of reporting restrictions inside Syria.

The air raids, which come as government troops press an advance into the eastern and northern parts of the city, have prompted a mass exodus of civilians, Rami Abdel Rahman, head of the Britain-based Syrian Observatory, said.

"Residents of the eastern neighbourhoods began fleeing about three days ago as the pace of the barrel bomb attacks increased," he told AFP news agency.

Barrel bombs have killed more than 700 people in Syria in the past six weeks. Their use has been denounced as indiscriminate, not least by Western powers at last week's peace talks in Switzerland.

Western powers proposed a UN Security Council resolution in December to condemn the use of barrel bombs, which they say indiscriminately target civilians.

But Russia, a staunch ally of President Bashar al-Assad, has repeatedly blocked such plans in the Security Council.

Once Syria's economic hub, large parts of Aleppo have been devastated by the fighting that began there in mid-2012. The city is split into areas held by regime and rebel forces.

The reports of fresh attacks came as a UN-organised meeting of key international players in Rome endorsed a dozen steps to ensure immediate humanitarian relief.

Valerie Amos, the UN humanitarian chief, did not give details about the actions, saying only that they involved "access to besieged communities, access to hard to reach areas, demilitarisation of schools and hospitals'' and progress on funding.

The meeting, attended by international organisations and state representatives, follows a summit in Kuwait, where nations pledged more than $2bn to aid. The UN has set a target of more than $6bn.

Al Jazeera's Jacky Rowland, reporting from Rome, said the the UN was looking at a grim future for Syria.

"We are going to have more violence, and more people displaced," she said. "There are already two million refugees, most in neighbouring countries, and they expect that number to double by the end of the year.

"There is also a big question about who is giving these people protection. There have been repeated calls for wealthy nations to open their borders to refugees."