Thailand’s army chief has announced that the military is taking control of the government and has suspended the constitution.
In a televised statement, Gen Prayuth Chan-ocha said the military would restore order and enact political reforms in the South-East Asian nation.
The coup came after two days of inconclusive talks between the main political factions.
Thailand has been in political turmoil for months.
On Tuesday the army imposed martial law.
A curfew has now been declared, effective across the country from 22:00 to 05:00 local time.
Political party leaders, including opposition leader Suthep Thaugsuban, were taken away from the talks venue after troops sealed off the area.
Troops have reportedly fired into the air to disperse groups of rival supporters.
Gen Prayuth said in his TV address: “In order for the situation to return to normal quickly and for society to love and be at peace again… and to reform the political, economic and social structure, the military needs to take control of power.”
The latest unrest began in the Thai capital late last year, when then-Prime Minister Yingluck Shinawatra dissolved the lower house of parliament.
Demonstrators have blockaded several areas of Bangkok for months.
Earlier this month, a court ordered Ms Yingluck’s removal for alleged abuse of power.
Thailand has faced a power struggle since Ms Yingluck’s brother, Thaksin Shinawatra, was ousted by the military as prime minister in 2006.
Mr Thaksin and Ms Yingluck have strong support in rural areas and among poorer voters.
Correspondents say they are hated by an urban and middle-class elite who accuse them of corruption and abuse of power.