More than 300 people were sued and seven people were arrested in connection with arson attacks on houses of ethnic minorities in Longadu upazila of Rangamati on Friday.Rangamati Police Super Saed Tarikul Islam confirmed it on Saturday.Upazila administration on Friday noon imposed section 144 of CrPC in the upazila as the supporters of Awami League attack on ethnic people over killing of a leader of the Juba League, the youth wing of the ruling party.The dead body of Md. Nurul Islam Nayon, 35, organizing secretary of Longadu sadar union Jubo League, was recovered from Chaar Mile area adjacent to the Khagrachhadi-Dighinala road on Thursday noon.He, son of late Fayez Ahmed of Baitta Pada area in the upazila, was a motorcycle driver. Two ethnic-minority people hired him to go to a spot. Later he was found dead.When the body was brought at Baitta area, the local leaders and the activists of Awami League, Juba League and Chhatra League took out a rally to the upazila in protest of the killing. The agitated persons from the rally attacked on minorities, vandalized and set their homes on fire.