BEIRUT (Reuters) - The Syrian army said on Wednesday it had cut off all supply routes into eastern Aleppo, and the government air-dropped thousands of leaflets there, asking residents to cooperate with the army and calling on fighters to surrender.

Residents inspect a damaged site after an airstrike on Aleppo's rebel held Al-Mashad neighbourhood, Syria July 26, 2016. REUTERS/Abdalrhman Ismail

President Bashar al Assad’s initiative comes a day after the United Nations said it hopes to restart peace talks in August.

Previous attempts at a diplomatic solution to end Syria’s five-year-old civil war collapsed in April, partly due to an uptick in violence in Aleppo.

On Tuesday, the army texted residents to ask them to leave the city and to give up their weapons.

Concern for those trapped in the rebel-held part of Aleppo is rising. The U.N. aid chief asked on Monday for weekly 48-hour pauses in fighting to allow food and aid to be delivered.

Once Syria’s largest city, Aleppo has been divided between rebel-controlled and government-held sectors all through the civil war. Taking full control of the city would be a significant victory for Assad.

An advance by pro-government forces around the only remaining supply route into the eastern sector this month enabled them to fire on it at close range, making the battlefront Castello road too deadly to use and putting at least 250,000 people in rebel-held districts under siege.

“(Armed forces) have cut all supply routes and crossings which terrorists used to bring mercenaries, weapons and ammunition into the eastern neighborhoods of Aleppo,” a statement from the Syrian military general command said.

The government refers to all rebels as terrorists.

The Britain-based Syrian Observatory for Human Rights said eastern Aleppo had been under effective siege since July 11, and advances in recent days by pro-government forces had strengthened their control of the only route in.

“Today there is no way at all to bring anything into Aleppo,” Observatory Director Rami Abdulrahman said.