The five were arrested under Malaysia's harsh Internal Security Act (ISA) in 2002 and accused of being involved with the Jemaah Islamiyah (JI) organisation, the Abolish ISA Movement said in a statement.
It called their imprisonment "a flagrant violation of human rights" and urged Malaysia not to renew the suspects' two detention orders, which expire this month.
"Extending the detention orders will imply that the recent administration is no different from the old regime," it said.
The government of Prime Minister Abdullah Ahmad Badawi, who took over when Mahathir Muhammad retired in October 2003 after 22 years in power, must "charge them in an open court" or "release all five detainees without delay and without conditions," the group said.
Malaysia is holding more than 80 suspects under the ISA, which allows for two-year detention periods that can be renewed indefinitely.
Scrapping of law
Rights groups have urged the government to scrap the legislation, but it maintains that detention without trial is needed as a first line of defence against what it calls terrorism.
The Abolish ISA Movement had earlier announced a six month campaign where former deputy prime minister Anwar Ibrahim will be the key speaker joined by other victims of the oppressive law.
Former PM Mahathir Muhammad
retired after 22 years of rule
Anwar said he had no sympathy for suspects if there was evidence against them but added: "We should not allow this terrorism bogey to be used as a pretext by authoritarian regimes to suppress or oppress them."
In the past, Malaysia regularly came under fire from Western governments over detention without trial, but criticism has been muted since the 11 September 2001 attacks in the US that led some countries to impose similar laws.