At least six bombs have exploded in central Bangkok, killing two people and injuring more than 20 others.
The bombers struck the capital as Thais celebrated the New Year on Sunday evening.
A senior police spokesman said that the largest bomb had apparently exploded outside a shopping mall near the Victory Monument in the city centre.
Fifteeen people were reported to have been injured in that explosion.
Two people were wounded when another bomb exploded near a police booth while five more people were hurt by an explosion in market.
The police said they were inspecting other locations where other bombs may have been placed.
The police have not yet said who had set off the bombs and no group has so far claimed responsibility.
Members of Thailand's Muslim minority are fighting a campaign for a separate Islamic state.
In recent months they have killed several Buddhist teachers, monks and bystanders in mainly Muslim areas of southern Thailand.
More than 1,400 people have been killed in the conflict since fighting began in January 2004.