BANGKOK (AFP) - A Thai man was shot dead and three others were injured as political protests in Bangkok turned violent on Saturday, police said, after opposition protesters vowed a final push in their bid to topple the government.

"A 21-year-man was shot dead by two bullets to his left side," said Boonchuay Pochantong, an official at a police station near a Bangkok sports stadium where unrest broke out earlier. He added that three more men were injured.

The circumstances were unclear but the shootings came after a mob of opposition protesters attacked government supporters travelling to a rally at the stadium in a show of support for embattled Prime Minister Yingluck Shinawatra.