Twenty inmates died in the central prison of Syria's northern Aleppo province over the past four days as a result of rebel siege, the state SANA news agency reported on Monday.

The rebel siege had prevented the Syrian Red Crescent from delivering aid to the prison, the report said.

Rebel fighters have surrounded the prison for over a year, and made repeated attempts to storm it with no avail.

The latest attack occurred last week when a large number of radical groups attempted to free their fellow fighters. They were pushed back by the Syrian military.