Justice Minister Wijeyadasa Rajapakshe said that the suspects are part of the 59 people who were identified as those not carrying serious charges against them and there is no threat to national security by their release.
Earlier, 39 suspects, detained on terrorism charges, were released on strong bail conditions, Rajapakshe told reporters.
The 20 suspects who are due to be released have accepted guilt, the Minister added.
The Sri Lankan government takes full responsibility to ensure national security, Rajapakshe said, responding to criticism from the former president Mahinda Rajapaksa.
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Those held under the PTA staged a hunger strike in mid October. They ended the strike following an undertaking by President Maithripala Sirisena to expedite their cases by early this month.
They wanted fast track hearing of their cases they had been held over a long time. Tamil rights groups dubbed them political prisoners and demanded their early release.