Bahrain will hold a second round of by-elections on October 1 in nine of 18 constituencies, authorities announced on Sunday, the day after polls that were boycotted by the Shiite opposition. The elections were held to replace 18 MPs of the main Shiite opposition formation Al-Wefaq, who resigned in February shortly after protests triggered a deadly response from the authorities in the Sunni-ruled Gulf kingdom. Four deputies were elected in the absence of any competitors, and five seats were allocated at the end of Saturday's elections, a government statement said. In the remaining nine districts, "no candidate received 50 percent of the vote", necessitating a second round, the statement added. The first round was held Saturday in an atmosphere of great tension, The opposition reported a low voter turnout, but the government said 51 percent of eligible voters had cast ballots. The interior ministry said that 22 people were arrested for attempting to obstruct the vote by closing roads, damaging cars in a parking lot near a polling station or by pouring oil in front of another.