Colombo:Sri Lankan investigators on Saturday arrested an Army Intelligence Unit official over the murder of a popular editor, Lasantha Wickremetunga, police said. The arrest came months after police sought public assistance in tracking down the suspects connected to the killing, Xinhua news agency reported. In February, the police released sketches of two suspects. Wickrematunge was the founding editor of the privately-run Sunday Leader newspaper. He was shot dead in January 2009 by a group of unidentified men in a high-security zone. He was a staunch critic of then President Mahinda Rajapaksa, who denied any role in the editor's killing. President Maithripala Sirisena, who took power in January 2015, had reopened investigations into Wickremetunga's murder, vowing to commence a thorough probe and arrest all those involved in the killing.