The UN Security Council has unanimously approved a resolution demanding a 30-day ceasefire across Syria “without delay” to deliver humanitarian aid to millions and evacuate the critically ill and wounded.

The sponsors, Kuwait and Sweden, amended the resolution late on Friday in a last-minute attempt to get Russian support, dropping a demand that the ceasefire take effect in 72 hours.

Russia’s UN Ambassador Vassily Nebenzia had said repeatedly that an immediate ceasefire was unrealistic.

Sweden’s UN Ambassador Olof Skoog said before the vote that the resolution could de-escalate violence and save lives.

“The UN convoys and evacuation teams are ready to go,” he said.

As she headed into the meeting, US Ambassador Nikki Haley said: “Today we are going to see if Russia has a conscience.”

There is no set time for the ceasefire to take effect, but the resolution demands that it be followed immediately by access for humanitarian convoys and medical teams to evacuate the critically ill and wounded.

The resolution states that 5.6 million people in 1,244 communities are in “acute need”, including 2.9 million in hard-to-reach and besieged locations.

It calls for all parties to immediately lift the sieges of populated areas including eastern Ghouta, Yarmouk, Foua and Kefraya.

The Security Council authorised one exemption from the ceasefire.

It said attacks directed at extremists from the Islamic State group and all al Qaida affiliates, including the Nusra Front, will be allowed to continue.

The move came after a new wave of air strikes and shelling on eastern suburbs of the Syrian capital Damascus left at least 22 people dead and dozens wounded, raising the death toll of a week of bombing in the area to 500.

The weeklong bombardment has overwhelmed rescuers and doctors at makeshift hospitals, many of which have also been bombed.

Activists say that terrified residents have been hiding in underground shelters where dozens of people can be crammed into small places.

Russia has been a main backer of Syrian President Bashar Assad since the country’s conflict began seven years ago.

In 2015, Moscow joined the war on Mr Assad’s side tipping the balance of power in his favour.

Syrian opposition activists say Russian warplanes are taking part in bombarding Damascus’ eastern suburbs, also known as eastern Ghouta, where many people are hiding in underground shelters with little food and medical supplies amid a tight government siege.

“There is no electricity, no water, no flour, no bread and no baby formula,” said paramedic Siraj Mahmoud in an audio message calling for a short break in air strikes so residents can get food for their children. “There is nothing inside Ghouta.”

Syrian UN Ambassador Bashar al-Ja’afari, centre left, enters the UN Security Council chambers before the vote (Craig Ruttle/AP)
Syrian UN Ambassador Bashar al-Ja’afari, centre left, enters the UN Security Council chambers before the vote (Craig Ruttle/AP)

Syrian opposition activists said that government forces used phosphorous bombs in their attacks on the suburbs, but the claims could not be independently confirmed.

The Britain-based Syrian Observatory for Human Rights said air strikes that hit several suburbs left 22 people dead in different areas, including 10 in the suburb of Douma.

The opposition’s Syrian Civil Defence, also known as the White Helmets, said 23 people were killed.

The Observatory said that since the latest wave of bombardment began on Sunday, 510 civilians, including 127 children and 75 women, have been killed in eastern Ghouta.

The White Helmets said it has documented the names of 420 people who have been killed since Sunday, adding that dozens more have still not been identified.

Syrian state media reported that rebels fired mortar shells on Damascus, Mr Assad’s seat of power, killing at least one person and wounding seven.

AP