GENEVA — On Wednesday, the United Nations mediator for Syria, who held talks with President Bashar al-Assad this week, condemned the government’s heavy bombing of civilian areas near Damascus and deadly rebel attacks on Aleppo.

U.N. special envoy Staffan de Mistura called on both sides to allow greater access to besieged areas, especially in view of the holy Muslim month of Ramadan. He also reiterated the need for a political settlement.

De Mistura, in meetings with Assad and Foreign Minister Walid al-Moualem, “underlined once again that the use of barrel bombs is unacceptable, and that it is an obligation under international humanitarian law for any government, in all circumstances, to protect its civilians,” the statement said.

He condemned the “heavy bombings by government forces last (Tuesday) night on Douma, which caused significant casualties.”

De Mistura and government officials also discussed “the increasing threat of advances by terrorist organizations.”

The U.N. envoy also condemned attacks on civilians by opposition forces, including on the northern city of Aleppo on Monday and a mortar shelling that hit central Damascus on Tuesday.

More than 30 people were killed in the most lethal rebel bombardment of Aleppo since Syria’s conflict started said on Tuesday.