Amnesty International welcomed the release of six political activists, but called on the Malaysian authorities to free thousands of other detainees held under preventive detention laws.
Socialist Party MP Dr Jeyakumar Devaraj and five party officers were held without charge for over a month under Emergency Public Order and Prevention of Crime Ordinance (EO), which allows for indefinite detention without charge or trial.
All six were travelling to an event related to a widely publicized demonstration on electoral reform in Malaysia when police arrested them.
The activists, known as the E06, were released from Jinjang police station today, following daily protests by local NGOs and international solidarity groups against their arbitrary detention.
"While the release of these six activists is welcome news, Malaysia should immediately release the thousands of people arbitrarily detained under this grossly unfair law," said Sam Zarifi, Amnesty International's Asia-Pacific Director.
"Preventive or arbitrary detention violates the right to a fair trial. Malaysia should respect this right instead of having a whole host of laws that punish people before they are even proven guilty in a court of law.
"There is no justification for Malaysian authorities still using these problematic preventive detention laws."
An estimated 2,000 people are currently detained without trial in Malaysia under the EO, which dates from the State of Emergency declared in 1969.
The EO has been used mainly to deal with suspected criminals who are regarded as difficult to bring to justice by the ordinary process of law.
On 9 July, police arrested 1,667 protesters at a peaceful electoral reform rally in Kuala Lumpur known as Bersih 2.0. All were released without charge later that night.
Around 40 people arrested ahead of the rally still face prosecution. Most have been charged under the Societies Act with possession of illegal materials, including Bersih T-shirts. If convicted, they could face five years in prison.
"Instead of responding substantively to the proposals for electoral reforms made by Bersih, Malaysia's government has arbitrarily detained political activists and supporters of Bersih in violation of their fundamental rights to freedom of association, expression, and peaceful assembly. This must stop," said Sam Zarifi.