More than 100 people were wounded after violence broke out at Negombo prison, north of Colombo, on Sunday and continued on Monday.
At least 20 people have been killed and more than 100 were wounded in clashes at a prison in Sri Lanka.
Violence broke out at the prison in Negombo, about 35km (22 miles) north of the capital, Colombo, on Sunday and continued on Monday, according to local media reports and police.
A hospital source told Al Jazeera that at least 16 inmates and four prison guards were killed in the violence.
Pushpa Gamlath, director of the Negombo hospital, said the facility had received 23 bodies and more than 100 wounded inmates and guards had also been admitted to hospital, the AFP news agency reported.
Police spokesman Chandana Herath confirmed the clashes in the prison and that there were deaths, without providing further details.
The reason for the clashes was not immediately clear.
Footage from Derana TV showed a heavy police presence outside the gate of the prison as a police bus carrying the injured inmates, some of them sprawled on its floor, left the premises.