The UN Secretary General has demanded an immediate end to fighting in the Eastern Ghouta in Syria, describing the rebel enclave as a “hell on earth”.
“My appeal to all those involved is for an immediate suspension of all war activities,” Antonio Guterres told the UN Security Council on Wednesday.
He said a ceasefire would allow humanitarian aid to reach the region.
The Eastern Ghouta has been under fierce bombardment from government forces in recent days.
The Syrian military says it is trying to liberate the area from what it terms terrorists – but it has also been accused of targeting civilians.
“I believe Eastern Ghouta cannot wait,” Mr Guterres said.
“This is a human tragedy that is unfolding in front of our eyes and I don’t think we can let things go on happening in this horrendous way.”
He said an end to the fighting would allow the evacuation of hundreds of people who require urgent treatment.
Russia has meanwhile called for an urgent Security Council meeting on Thursday to discuss the violence in the Eastern Ghouta.
Earlier on Wednesday, UN human rights commissioner Zeid Raad Al Hussein joined calls for an end to the conflict in the region.
“How much cruelty will it take before the international community can speak with one voice to say enough dead children, enough wrecked families, enough violence, and take resolute, concerted action to bring this monstrous campaign of annihilation to an end?” he said in a statement.
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 has a presence there.
Pro-government forces, backed by Russia, intensified their efforts to retake the last major rebel stronghold on Sunday night.
Since then, activists say nearly 300 people have died, more than 60 of them children. At least 1,400 people have been injured, they say.