The Kurdish-led Syrian Democratic Forces said its forces thwarted the escape attempt by prisoners that coincided with a car bomb that was detonated near the prison by militants.

Islamic State militants attacked a prison in Syria's al-Hasaka in an attempt to free prisoners belonging to the group who had mutinied, the Kurdish-led Syrian Democratic Forces (SDF) said in a statement on Thursday.

Islamic State "sleeper cells ... infiltrated from the surrounding neighborhoods and clashed with the internal Security Forces," the US-backed group added.

The SDF, which is spearheaded by the Kurdish YPG militia, said its forces thwarted the escape attempt by prisoners that coincided with a car bomb that was detonated near the prison by militants, spokesman Farhad Shami said in a tweet.

There were unconfirmed reports that 25 inmates had been killed in the mutiny, the latest of several recent attempts to flee from SDF prisons, according to two residents.

Arab tribal figures in touch with residents in the area said US coalition planes were seen flying overhead in the vicinity of the prison following the incident.

It was not clear how many inmates were in the prison, one of several where the SDF has kept thousands of detainees, many of whose relatives say are young children and others arrested on flimsy charges or for disobeying the SDF’s policy of forcible conscription.