An international human rights group urged Sri Lanka's government on Wednesday to release hundreds of prisoners held without charge under the country's tough anti-terror laws.
Amnesty International said some detainees are kept in secret locations where they are vulnerable to torture or even death in custody.
It said 1,900 people are being held without trial according to the most recent official reports.
"Sri Lanka's so-called national security laws, and in particular the PTA (Prevention of Terrorism Act), are being used to harass, intimidate and punish critical voices," said Sam Zarifi, the group's Asia-Pacific Director.
He said the detentions are "outside even the protections offered by the Sri Lankan legal system and in clear violation of recognized international human rights standards."
Some prominent journalists are among those who have been detained under the Prevention of Terrorism Act.
The law gives the police and military sweeping powers to enter and search premises without warrants, seize or seal off property, and detain people suspected of terrorism.
The London-based human rights group said it interviewed a detainee identified only as Elil who has spent 10 years in a Colombo prison without being charged.
Sri Lanka has spent a large portion of the last 40 years under emergency law. Tamil Tiger rebels fought the government for 26 years for an independent homeland for ethnic minority Tamils until they were defeated in 2009.
Authorities say the anti-terror laws are needed to detain captured rebels.