The Syrian police tear-gassed tens of inmates in a bid to quell a riot that engulfed the central prison of Syria's Hama city, Xinhua reported.
Citing "crosschecked sources," the Syrian Observatory for Human Rights said the Central Prison of Hama is witnessing a riot by inmates, who were detained without trials.
The UK-based watchdog group said it had received a video footage, showing inmates shouting and badmouthing the authorities inside the prison.
Activists said gunfire was heard in the vicinity of the prison, as the government forces succeeded in storming the jails and taking some of the prisoners to unknown destination.
The watchdog added that tens of inmates fainted as a result of the tear gas firing by the authorities.
The Syrian opposition accuses the government of detaining thousands of political activists without trials.
On Monday, the Syrian authorities released Mazen Darwish, one of the most prominent Syrian activists and human rights defender, who had been imprisoned in government jails since 2012 for his antagonism to the Syrian administration, according to the Observatory and local media reports.
Darwish, who is an outspoken critic of the government and has taken part in anti-government protests at the beginning of the conflict, was arrested in 2012 by the Syrian intelligence apparatus during a raid on his Damascus office.