An aide to the mayor of Mariupol said on Friday the besieged southern Ukrainian city remained closed for anyone trying to enter and was “very dangerous” for anyone trying to leave.

Petro Andryushchenko said Russian forces had since Thursday been preventing even the smallest amount of humanitarian supplies reaching trapped residents, making clear a planned “humanitarian corridor” had not been opened.

“The city remains closed to entry and very dangerous to exit with personal transport,” he said on the Telegram messaging app. “In addition, since yesterday the occupiers have categorically not allowed any humanitarian aid - even in small quantities - into the city.”

A convoy of buses that set out for Mariupol on Thursday did not reach the city, Ukrainian officials said on Thursday evening.

The Mariupol mayor said this week that up to 170,000 residents were trapped there with no power and dwindling supplies. Repeated attempts to organise safe corridors have failed, with each side blaming the other.

Russia denies attacking civilians in its assault on Ukraine that began on Feb. 24.

War in Ukraine: Latest developments

The governor of the Luhansk region in eastern Ukraine said separately that he hoped five safe corridors would be opened on Friday to towns and cities in his region.