The Rio Olympics have been unsettled by a loud blast near the cycling race’s finish line and a stray bullet being fired into the media tent at the equestrian venue.

Brazilian military were called to the men’s road race, where they carried out a controlled explosion near the Copacabana finish line.

The explosion shocked crowds who had gathered for the end of the race.

The race leaders were about 100 kilometres from the incident, with bomb disposal experts at the scene keeping crowds away.

Officials inspect damage to the media tent. Photo: Getty

Meanwhile, at the Deodoro venue, onlookers were shocked when a bullet ripped through the temporary venue housing media, leaving visible holes in the fabric roof and wall.

ABC reports that nobody was injured in the incident.

The equestrian venue is next to a military complex, though police are still trying to discover who fired the bullet and from where, a spokesman for the Rio 2016 organising committee said.

“It was a stray bullet and has nothing to do with the Games,” Mario Andrada said at a news conference, adding that security around the venue had been increased as a precaution.

It made for an unsettling day one of the Rio Games, which were launched in a blaze of colour by a flamboyant opening ceremony.

But in further violence, police gunned down a mugger outside the ceremony venue, the Maracana stadium, and a woman was shot and killed by armed assailants near the Olympic Boulevard.