Malaysia's government has proposed law changes that would allow crime suspects to be detained for years without trial.
Prime Minister Najib Razak's government proposed amendments to the 1959 Prevention of Crime Act, saying the police need strong powers to fight a wave of violent crime in recent months.
Najib had only just abolished such powers - which critics have long complained were abused by the authoritarian government to silence dissent - in 2011 in the face of public pressure for a more open society.
The opposition immediately branded the proposed amendment as a dangerous U-turn on rights.
"The government is setting back the clock and dragging us back to the era of arbitrary arrest and detention," N Surendran, a senior leader of the opposition People's Justice Party, said in a statement.
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Facing ebbing support for his long-ruling coalition and after large street protests for electoral reform, Najib in 2011 abolished the draconian Internal Security Act and the separate Emergency Ordinance (EO).
Both allowed lengthy detention without trial.
Najib sought to portray himself as a reformer before elections that were held this May, in which his coalition retained power.
However, the three-party opposition alliance stunned the government by winning a majority of the popular vote for the first time ever.
Malaysians have been shocked by an upsurge in gun violence in recent months that some government officials have blamed on criminals it said were put back on the streets after the EO was scrapped.
Conservatives in the ruling United Malays National Organisation have since campaigned for the return of wide-ranging preventive detention powers.
The opposition called for the proposed legislation, set for debate in parliament next week, to be withdrawn.
The government has "a long history of abusing preventive detention laws for political purposes", Surendran said.
