About 150 prisoners escaped Thursday from an overcrowded prison in western Indonesia, and others held officers hostage, following a riot triggered by a blackout.

Prison directorate spokesman Akbar Hadi said the inmates forced their way out from Tanjung Gusta Prison in Medan, the capital of North Sumatra province, while others set the prison's offices on fire.

National Police Spokesman Maj. Gen. Ronny Frengky Sompie, saying police were investigating media reports that 12 terrorist inmates were among those who escaped.

Hadi said about 15 officers were being held captive inside the prison. It holds about 2,400 prisoners but media reports say its normal capacity is 400.

The riot appeared to have been triggered by a blackout that knocked out the pumps that supplied water to the prison, leaving inmates without water since Thursday morning, Hadi said in a text message.

BeritaSatu TV station reported that the prisoners seized guns from the officers. Its reporter said gunshots were heard from inside the prison.

Thousands of policemen are deployed around the prison and the Indonesia's third largest town to blockade roads linking Medan and other provinces while fire brigades are battling the fires.

MetroTV station reported that at least 10 prisoners including a terrorist convict had been recaptured.