An explosion in Malaysia’s northern Penang State on Tuesday comes as the latest in a swelling of violence before hard-fought May 5 polls.

The blast occured near a political gathering of the ruling Barisan Nasional coalition, and wounded a security worker, police said Wednesday.

“It was a time bomb. But it did not contain any splinters or shrapnel,” local police spokesman Rosli Chik told AFP, adding that a second bomb was later found in the area and was detonated safely.

A total of 387 incidents were reported in the first three days since the official campaigning period started, according to AFP.

In one incident, rioters armed with weapons such as machetes reportedly slashed rival party supporters. At least 15 people have been arrested over the violence, national police spokesman Ramli Yoosuf told The Star newspaper, without giving any indication of who was committing the violence.

The opposition, however, has complained that its supporters have been victims in most of the attacks.

No deaths have yet been reported, but local media last week reported a man was left in a coma after he was allegedly beaten by ruling party supporters.

Malaysia is bracing for long-anticipated elections that have raised speculation on the country’s first change of regime since its independence from Britain in 1957.