A rare political protest in the Chinese territory of Macau turned violent after demonstrators clashed with police.
Some protesters said police fired live rounds of gun shots
Hundreds of people had been taking part in a May Day protest over alleged corruption and illegal labour.
Police fired shots into the air and used dogs to try to disperse the marchers, as they veered off the route.
Protesters were complaining about the lack of local jobs due to an influx of cheap foreign labour caused by a recent boom in Macau's lucrative casino trade.
They accuse the government of turning a blind eye to the situation.
Some protesters carried signs saying, "Severely punish employers of black market workers", while others called for Macau's political leaders to stand down.
"We are displeased with the labour crisis and the government's lack of action in dealing with it," said Ho Hen Kuok, president of the Macau Labour Union.
"We don't want to see illegal labour being given jobs."
"The government is rich, the casinos are rich, but nobody is looking out for the Macau people," one marcher told the AFP news agency.
The protest turned violent as demonstrators tried to break through the police cordons lining their route.
Protesters surrounded one police vehicle and threw water bottles and placards at officers, who had boosted their lines with water cannons, the AFP reports.
Police also fired shots into the air, but it was not immediately clear if they had used blank or live rounds to disperse the crowds.
There were no reports of injuries, but several protesters were seen being led away by police.
Unlike nearby Hong Kong - another former European colony which was returned to China in the 1990s - such protests in Macau are uncommon.
Macau's population of 500,000 has a history of co-operation with the Beijing government.
The tiny territory has seen a surge in investment in recent years, with foreign gambling firms - mainly from the US - moving in to build new casino resorts.
Macau workers say that a resulting labour shortage in the territory has led many employers to hire cheap illegal labourers from mainland China.