"The UN strongly condemns an attack on October 30 on the building where UN staff and offices are based in western Aleppo city," Dujarric told reporters. "The UN presence in the building is well-established and well-known."
Dujarric said the attack directly targeted the building, but the UN currently lacks forensics to pinpoint who is responsible for the shelling.
Additionally, he noted reports over the weekend of intensified shelling by opposition groups in government-held areas of western Aleppo had killed more than 30 civilians, including at least 10 children, and injured dozens more.
The increase in civilian casualties suggests that armed opposition groups are failing to follow the international prohibition against indiscriminate attacks, Dujarric said.
Earlier on Tuesday, a spokesperson for the UN High Commissioner for Human Rights said all parties to the conflict in Aleppo are conducting attacks that may amount to war crimes.