50-year-old Balendra Jeyakumari's release came days ahead of Prime Minister Narendra Modi's visit to the country.
Under bail orders, she has been prohibited from leaving the country by the Colombo Additional Magistrate which also asked her to report to police station closest to her residence every month.
Sri Lankan police had arrested Jeyakumari, a widow and a mother of four children from the former northern war zone of Kilinochchi on the charge of harbouring a man who shot at a police officer to evade arrest.
However, Tamil parties have alleged that she was being punished for protesting over the fate of her son, an underage rebel who disappeared after the Tigers surrendered to the government at the end of the war in May, 2009.
Jeyakumari and her daughter were at the forefront of protests over the fate of disappeared people when dignitaries visited Kilinochchi, including British Prime Minister David Cameron in November, 2013.
Her two sons were killed in the war and the third went missing after she handed him over to the military in May 2009.
Commenting on her release, Sri Lanka Campaign -- a civil society pressure group based in London -- said, “Jeyakumari's detention made it hard to accept the idea that there had been any meaningful change in Sri Lanka. Her release gives us greater cause for hope.”
“But the true test will be whether her release marks the beginning of a broader reversal in a pattern of harassment by the security forces against families of the disappeared and other Tamil activists in the north and east of Sri Lanka,” it said.
The group demanded the repealing of the Prevention of Terrorism Act under which she was held without a charge for nearly a year.
The court also released 6 other activists along with Jeyakumari.
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