Syrian President Bashar Al-Assad
Syrian President Bashar Al-AssadReuters

The UK-based Syrian Observatory for Human Rights said at least 21 people have been killed, 5 of them children, when Syrian airstrikes damaged a children's hospital, a blood bank, and a school in eastern Aleppo.

The Syrian government of Bashar al Assad announced on Tuesday that it was resuming airstrikes against rebel-held areas after the end of a three-week moratorium which had been declared by the government's ally, Russia.

Russia denied any involvement in the raids on Aleppo, and claimed that was still following its moratorium on airstrikes.

The bombardment caused a fire in the children's hospital, shutting the hospital down. A school and a blood bank were also struck in the al-Shaar district of Aleppo.

Ibrahim al-Haj of the White Helmets rescue civil defense organization, said that at least 40 air strikes were carried out. He added that an ambulance driver was also killed while trying to rescue victims of the al-Shaar district.

The director of the children's hospital appealed for help on Facebook.

"A horrible day for the Children's Hospital. Me and my staff and all the patients are sitting in one room in the basement right now, trying to protect our patients. We are trying to leave the basement but we can't because of all the aircraft still in the sky." wrote a man who identified himself as Doctor Hatem.

He said that the hospital had been hit by 20 barrel bombs and begged people to "pray for us."