The death toll from two days of bombing by Syria’s government of a rebel-held area has risen to 250, reports say.
It is the worst violence in the Eastern Ghouta area near Damascus since 2013, according to activists. More than 50 children are among the dead, they say.
The UN has warned that the situation is “spiralling out of control”.
Meanwhile the Damascus government has sent forces to confront Turkish troops who have crossed the border to push back the Kurds in northern Syria.
The Syrian military has not commented on the reports from the Eastern Ghouta, but said it carried out “precision strikes” on areas from which the shells were launched.
A UN spokesperson said at least six hospitals had been hit in the area on Monday and Tuesday.
What’s happening in the Eastern Ghouta?
The Eastern Ghouta is the last major rebel stronghold near Damascus. Pro-government forces – backed by Russia – intensified their efforts to retake it on Sunday night.
The Syrian Observatory for Human Rights, a UK-based monitoring group, said at least 250 had been killed in air strikes and artillery fire since then.
It said it the highest 48-hour death toll since a 2013 chemical attack on the besieged enclave. About 1,200 people have been injured.
Activists said at least 10 towns and villages across the Eastern Ghouta came under renewed bombardment on Tuesday.
The UN called for a ceasefire to allow humanitarian aid to be delivered and the wounded to be evacuated.
The horror reaches new extremes
By Sebastian Usher, BBC Middle East analyst
The people of the Eastern Ghouta have suffered devastation many times before, but little on this scale.
It is not just the human cost, but the targeting of the last vestiges of the area’s infrastructure.
The UN says six hospitals have been hit – making it even harder to treat the latest victims – while schools and homes have been bombed.
The message from the warplanes in the sky seems to be that there is nowhere left to hide – the government’s long war of attrition now taken to the extreme in a final effort to force the surrender of this last rebel bastion on the fringe of Damascus.
The usual chorus of international outrage is rising once again, but so far with no effect. The UN’s children’s agency simply issued a blank statement, saying it had no words left to do justice to the horror.
How bad is the situation in the enclave?
A local doctor told the Union of Medical Care and Relief Organisations (UOSSM), which supports medical facilities in the Eastern Ghouta, that it was “catastrophic”.
“People have nowhere to turn,” he said. “They are trying to survive but their hunger from the siege has weakened them significantly.”
The UN’s co-ordinator in Syria, Panos Moumtzis, said he was “appalled” by reports that hospitals had been deliberately targeted, warning that such attacks might amount to war crimes.
Five hospitals in Marj, Saqba and Douma were left inoperable or partially functioning after reported government strikes on Monday, while on Tuesday a hospital in Zamalka was hit, according to Mr Moumtzis.
The Syrian American Medical Society (SAMS) said a hospital in Arbin was also put out of service on Tuesday. The Syrian Observatory said the facility was targeted by Russian warplanes.
The government has allowed one humanitarian convoy into the Eastern Ghouta since late November, and there are severe shortages of food.
A bundle of bread now costs close to 22 times the national average and 12% of children under five years old are said to be acutely malnourished.
The Eastern Ghouta is dominated by the Islamist faction Jaysh al-Islam. But Hayat Tahrir al-Sham, a jihadist alliance led by al-Qaeda’s former affiliate in Syria, also operates there.
The region has been designated a “de-escalation zone” by Russia and Iran, the government’s main allies, along with Turkey, which backs the rebels, but hostilities intensified in mid-November.