UNITED NATIONS — United Nations Secretary-General Ban Ki-moon warned on Tuesday of an unprecedented “humanitarian catastrophe” in Syria’s Aleppo and urged Russia and the United States to quickly reach a deal on a ceasefire in the city and elsewhere in the country.

Fighting for control of Aleppo, split between its government-held west and rebel-held eastern neighborhoods, has intensified in recent weeks, causing hundreds of deaths and depriving many civilians of power, water and vital supplies.

“In Aleppo, we risk seeing a humanitarian catastrophe unprecedented in the over five years of bloodshed and suffering in the Syrian conflict,” Ban told the U.N. Security Council in his latest monthly report on aid access, seen by Reuters.

Ban said the fight for territory and resources is being undertaken through indiscriminate attacks on residential areas.

“All parties to the conflict are failing to uphold their obligation to protect civilians,” Ban said in the U.N. report.

Ban reiterated a U.N. call for at least a 48-hour humanitarian pause in fighting in Aleppo for aid deliveries and also pushed Moscow and Washington to rapidly reach a deal on a ceasefire.

Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry on Tuesday discussed securing a ceasefire, the Russian Foreign Ministry said.

On Thursday, the Russian military said it’s ready to back a U.N. call for weekly 48-hour cease-fires to allow humanitarian aid deliveries to the embattled Syrian city of Aleppo.

The president of the International Committee of the Red Cross, Peter Maurer, has described the fight for the Syrian city of Aleppo as one of the most devastating conflicts in modern times. 

“No one and nowhere is safe,” he said. “Shell-fire is constant, with houses, schools and hospitals all in the line of fire. People live in a state of fear. Children have been traumatized. The scale of the suffering is immense.”