Officials say security forces fired tear gas at protests that turned violent after opposition marchers started throwing stones in Guinea's capital.

Government spokesman Albert Damantang Camara said Wednesday that at least 18 security personnel were injured. Opposition spokesman Mouctar Diallo said at least 9 Guineans were also injured.

Police official Capt. Lamine Sano said police tried to disperse those demonstrating because they feared further violence. He said opposition supporters were marching and throwing rocks in a Conakry neighborhood that is home to the ruling party.

A spokesman for Guinea's opposition said that it has withdrawn from the upcoming legislative election set for May 12 because the opposition is unhappy with preparations for the election.

President Alpha Conde was elected in 2010, but the vote for the legislature has been delayed.