A bomb at a bus stop in Bangkok injured nine people shortly after polls closed in a parliamentary election today.
The poll pitted a government candidate against a jailed leader of recent mass protests in the Thai capital.
Police spokesman Anuchai Lekbamroong, at the site of the explosion, declined to speculate whether the bombing was related to Thailand's continued political turbulence in the wake of the street demonstrations that paralysed much of the capital for weeks.
The bomb wounded eight Thai people and one woman from Burma, the police officer said. The explosion was near two department stores that have been closed since they were torched at the climax of the protests May 19.
"I was selling drinks when I heard an explosion," said Urai Wiengsong, a street vendor near the bus stop.
"Then people started running off in different directions. I heard men and women scream and shout."
Before the explosion, he said, "People stood at the bus stop, waiting for buses. It looked normal."
Meanwhile, the government candidate appeared on his way to a narrow victory over a contender being held in jail on terrorism charges in an election touted by rival sides as a barometer of Thailand's political climate, according to preliminary results.
The poll was seen as a test of strength for the Red Shirt movement, which from March to May staged demonstrations that were finally put down with lethal force.
The protesters had demanded that Prime Minister Abhisit Vejjajiva dissolve parliament and call a general election.
In the by-election, Panich Vikitsreth, a vice minister for foreign affairs with the ruling Democrat Party, so far had 53% of the vote over rival Kokaew Pikulthong, an imprisoned Red Shirt leader, unofficial results from the Election Commission said.
The results represented about half of the ballots counted.
An exit poll by Suan Dusit polling company indicated that Mr Panich would emerge the winner.
Mr Kokaew had to campaign from his prison cell, where he is held on terrorism charges for his alleged role in the violent end to the protests. He was contesting a vacant seat in the House of Representatives for the opposition Pheu Thai Party.
"This by-election is Bangkok residents' referendum on the government," said Pheu Thai spokesman Prompong Nopparit before the election. The Democrats made a similar statement.
Thailand has been in a state of political turmoil since 2006, when a coup ousted then-Prime Minister Thaksin Shinawatra, who was popular among the rural and urban poor.
Since then, his supporters and opponents have staged a bitter struggle for power.
The Red Shirts, made up of Thaksin's supporters and other opponents of the coup, staged protests in April last year and then relaunched their campaign against Abhisit in March this year.
An escalating series of confrontations ended on May 19, when the army moved in to sweep the Red Shirt demonstrators from the streets.
Over two months, almost 90 people died - most of them protesters killed by authorities - and more than 1,400 were hurt in politically related violence. More than 30 buildings were torched.
A state of emergency is still in effect, and the top protest leaders are in detention.
The Pheu Thai Party is closely aligned with the Red Shirt movement by way of their shared support for Thaksin, who is in self-imposed exile after fleeing ahead of a corruption conviction in 2007.
Pheu Thai points out handicaps under which it campaigns - generally hostile mainstream media, censorship of its own print, broadcast and internet organs, and Kokaew's detention.
The constituency where the election took place is considered Democrat territory, and the party also counted on a backlash caused by the violence associated with the Red Shirt movement.
But during the protests it was clear that many in Bangkok supported or were at least sympathetic to the Red Shirt cause of greater social and economic equality.