GENEVA (AP) — The U.N. special envoy for Syria on Friday urged Russia to leave the creation of any humanitarian corridors around the embattled northern Syrian city of Aleppo to the United Nations and its partners.

"That's our job," said Staffan de Mistura as he explained his "suggestion" to Moscow at a press conference in Geneva, a day after Russia said its forces and those of the Syrian government would open humanitarian corridors outside Aleppo and offer a way-out for fighters wanting to surrender.

Earlier on Friday, Syrian activists said a U.S.-led coalition targeting a village in northern Syria held by the Islamic State group had killed 28 civilians the previous night, including seven children.

In Geneva, de Mistura expressed support "in principle" for humanitarian corridors "under the right circumstances." He said he is awaiting clarification from Russian authorities about that plan, noting the urgent situation in the northern city, wracked by devastating violence in recent months.

The envoy also warned that "the clock is ticking for the Aleppo population."

"How do you expect people to walk through a corridor — thousands of them — while there is shelling, bombing, fighting?" de Mistura said.

He added that no one should be forced to leave Aleppo, but "indeed, some civilians may want to avail themselves of the possibility afforded by the corridor and by the Russian initiative. When they do, it is crucial that they be given the option of leaving to areas of their own choice."

De Mistura also praised a statement from the international Red Cross about the Russian proposal, which said any such corridors should have the "consent of all parties on all sides." ICRC regional director for the Mideast, Robert Mardini, said Friday he had no indication all sides were on board with the plan.

According to the Britain-based Syrian Observatory for Human Rights, aircraft belonging to the coalition struck the village of al-Ghandour late on Thursday, killing the 28. Observatory chief Rami Adurrahman said another 13 people were killed in the strikes but that he could not say if they were IS fighters or civilians.

Al-Ghandour is 24 kilometers (15 miles) northwest of the town of Manbij, a key hub in the extremist group's Syria network and a supply route to IS's de facto capital of Raqqa.

The international coalition had no immediate comment on the casualty figures reported by the Observatory. The bombings came a week after airstrikes, also blamed by Syrian activists on U.S. aircraft, killed at least 56 civilians in Islamic State-held territory in northern Syria.

The Manbij area has seen extensive battles between IS extremists and U.S.-backed Kurdish-led fighters, who have been advancing under the cover of airstrikes by the U.S.-led coalition. The town is encircled by the Kurdish-led forces.

The Kurdish-led forces were able to evacuate another 1,000 civilians from Manbij Thursday, according to Mustafa Bali, a local media activist living in the town of Kobani.

"There has been a lot of pressure on the militants in Manbij," said Bali.

Late Thursday, the U.S. Central Command, which is responsible for U.S. forces in the Middle East, said in a statement that the American-backed coalition had conducted airstrikes in the area of Manbij during the past 24 hours and that it was looking into whether an airstrike had resulted in civilian casualties.

It was not clear if the Manbij-area strikes that CENTCOM cited involved strikes on al-Ghandour.

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Issa reported from Beirut.