Sri Lankan authorities said that Buddhist groups were likely to blame for a wave of anti-Muslim riots that swept the island this week in apparent retaliation for last month's Easter bombings.The April 21 attacks, claimed by the Islamic State of Iraq and the Levant (ISIS), targeted churches and hotels, killing more than 250 people and heightening fears of a backlash against the nation's minority Muslims.In the anti-Muslim unrest that started Sunday, mobs moved through towns in Sri Lanka's northwest, ransacking mosques, burning Korans and attacking shops with petrol bombs, residents said.Authorities have arrested dozens of suspected rioters, including three described as Sinhala Buddhist hardliners who had been investigated for similar actions in the town in Kandy district last year."These are organised attacks on Muslim business houses and premises," Navin Dissanayake, minister of plantation industries, said during a government news conference on Wednesday about the security situation.Asked who was organising the attacks, Dissanayake said: "I think these organisations that Amith Weerasinghe, Dan Priyasad, and Namal Kumara (are heading)," referring to the three Buddhist hardliners arrested on Tuesday. 190427114108184 Local media reported on Wednesday that Priyasad was released on bail on Wednesday while Weerasinghe was remanded until May 28. The status of Kumara was not clear, according to the Reuters news agency.Muslims make up nearly 10 percent of Sri Lanka's population of 22 million, which is predominantly Buddhist. The Indian Ocean island was torn for decades by a civil war between separatists from the mostly Hindu Tamil minority and the Sinhala Buddhist-dominated government. The government stamped out the rebellion about 10 years ago.In recent years, Buddhist hardliners, led by the Bodu Bala Sena (BBS) or "Buddhist Power Force" have stoked hostility against Muslims, saying Middle Eastern influence has turned the community more conservative and insular.'Political aims'In the same press conference, Ranjith Madduma Bandara, minister of public administration, said the group behind the attacks had political aims."This group is trying to tarnish the government's image and show the government is unable to handle the situation," he said, without naming the organisation.Authorities said the island was calm again, with no anti-Muslim violence reported on Wednesday. 190513144625670 Also on Wednesday, Sri Lanka's army said it was investigating a video posted on social media that showed a man wearing what appears to be an army uniform walking away seconds before an anti-Muslim mob attacked a building this week.In the video, the man stands outside the building and then leaves. Seconds later, about two dozen people, including young men wearing motorbike helmets, run over and throw stones at the building.Al Jazeera could not independently verify the video."The attention of the army has been drawn to a video clip where a person dressed in uniform similar to that of the army was watching while a group of violent saboteurs were in action in the general area of Thunmodara," the army said in a statement announcing the investigation.