At least 90 people have been killed in overnight air strikes by the Syrian government and Russian forces across Syria, according to monitors and opposition activists.

Most people were killed around Aleppo province, where more than 300,000 civilians are trapped in rebel held territories.

The air raids hit the only hospital for women and children in the town of Kafr Hamra, killing two members of staff, including a nurse, while 10 people were rescued from the rubble, the Syrian Civil Defence said.

Air strikes also hit a market in the nearby town of Urem al-Kubra, killing at least six people, according to the UK-based Syrian Observatory for Human Rights.

Urem al-Kubra lies on the road linking Aleppo to the northern rebel-controlled province of Idlib, which has also seen intense bombing.

"This is one of the highest death tolls we have seen in the recent days," said Al Jazeera's Reza Sayah, reporting from Gaziantep on the Turkish side of the Syria-Turkey border.

Russia's military announced a three-hour daily halt in air strikes in Aleppo to allow humanitarian convoys in on Thursday, but the UN said it was not nearly long enough to help trapped civilians.

"The grim statistics came on a week in which the UN, international community renewed its call about the pause in fighting in order to get some aid to the people who desperately need it," our correspondent said.

"These statistics, this death toll, is an indication that no one is hearing these calls."

READ MORE: ISIL flees Manbij with 'human shields'

In another development, the Islamic State of Iraq and Levant (ISIL) group has released more than 2,000 people they had been using as human shields after fleeing Manbij, a city in Aleppo province.

The Syrian Democratic Forces (SDF), a US-backed alliance consisting of Kurdish and Arab fighters, said on Friday that they were in control of most of the city, which had been held by ISIL, also known as ISIS, since 2014.

"While withdrawing from a district of Manbij, Daesh jihadists abducted around 2,000 civilians from al-Sirb neighbourhood," Darwish told AFP news agency, using an Arabic acronym for ISIL.

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"They used these civilians as human shields as they withdrew to Jarabulus, thus preventing us from targeting them," he said, adding that women and children were among those taken.

Darwish later told the Reuters news agency that the SDF had freed more than 2,000 civilian hostages.

"Now there are reports that these civilians have been released, there is a video posted online showing civilians celebrating," Al Jazeera's Sayah said.

The UN says Russia is willing to discuss its proposal of a 48-hour ceasefire to deliver aid to thousands of Syrians without food, water and medicine in Aleppo.