At least 20 members of Tanzania's main opposition party, including an MP, were released on bail on Monday after being arrested over the weekend, police said. Chadema party secretary general Vincent Mashinji had earlier said the group was arrested on Saturday over claims they were "fomenting trouble", but police gave no details of the charges.Mashinji confirmed their release on Monday. Lawmaker Frank Mwakajoka was arrested in his office in southern Tunduma after requesting forms for his party's candidates to take part in partial municipal elections in August, according to the party."We don't understand the reasons behind this arrest," Mashinji said, adding that police had arrested "20 other members of Chadema who were gathered in a local office of the party to prepare (for the) election"."According to the initial information we have, the police are saying they were fomenting trouble," he added.Chadema regularly accuses the police of making up charges against its members, with the aim of weakening the party, which the interior ministry denies. In September 2017, Chadema lawmaker Tundu Lissu was shot several times at his home, and in February two local Chadema officials were killed by unknown gunmen, in murders described by the opposition as political assassinations.