A Thai man was shot dead and three others were injured as political protests in Bangkok turned violent 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.

It was reporter earlier that Thailand will deploy nearly 3,000 troops to reinforce security in Bangkok, a senior police official said Saturday, with tensions rising as opposition protesters vow a final push in their bid to topple the government.

"From tonight there will be soldiers out to take care of security," national police spokesman Piya Utayo said in a televised address, adding that some 2,730 military personnel from the army, navy and airforce would take part.