The real killers will go unpunished unless an impartial investigation is ensured, she said at the 'Blue for Peace' programme at the Science Laboratory intersection in the city.

Initiated by Asma Kibria, the 'Blue for Peace' programme is being held every Thursday to demand trial of the killers of Kibria and others who died in bomb and grenade attacks across the country.

"We have no trust in the present investigation into the Kibria killing case as it was carried out to save the real killers," Asma said.

The government has brought a night guard, a driver and local BNP leader Qaiyum under the focus of the investigation, but the masterminds still remain free, she added.

"We have appealed to the United Nations to carry out a probe and also requested US Assistant Secretary of State for South Asian Affairs Christina Rocca during her visit to Bangladesh last week to help get the support from the US and the UN members to the UN investigation," Asma said.

She also vowed to continue the peaceful protest programme unless the real killers are brought to justice.

Family members of Kibria, members of civil society and common people joined the 'Blue for Peace' programme.

Kibria, also an Awami League leader, was killed in a grenade attack at Boiddyerbazar in Habiganj on January 27 last year.