BANGKOK — Antigovernment protesters clashed on Wednesday with security forces who fired their weapons in a short, sharp encounter on the edge of the city.
One soldier was killed and at least 18 people were injured, according to the government-run Erawan Medical Center.
Standing behind coils of razor wire and taking aim from behind concrete pilings, troops fired into the air and into the crowd to disperse the protesters, who had arrived in a long convoy of motorcycles and trucks
The Associated Press reported that witnesses said the soldier appeared to have been shot by other security forces.
Earlier in the day, an army spokesman, Col. Sansern Kaewkamnerd, said that soldiers mostly used rubber bullets but were authorized to use live ammunition in self-defense.
Protesters charged the razor wire and threw rocks and bottles, some of them from a highway overpass near Bangkok’s second-largest airport, Don Muang.
The encounter came after the protesters — who have largely discarded their trademark red shirts — made a rare foray from their camps in the center of Bangkok, where they have forced the closing of shopping malls and major hotels.
The protesters, who mostly represent the rural and urban poor and whose demonstrations have paralyzed parts of the capital for nearly seven weeks, say they will not relent until the government of Prime Minister Abhisit Vejjajiva resigns and holds a new election. At least 26 people have been killed in the protests.
Many support the fugitive former prime minister Thaksin Shinawatra and say they were robbed of their votes when he was ousted in a coup in 2006 and when later governments aligned with him were removed through court rulings.
The government has responded that it was duly elected by a parliamentary vote and that it will not give in to street protests.
The city is tense, with daily rumors of a military crackdown.
On Tuesday, soldiers in body armor set up command posts at several points in the city after the protesters said they would set out Wednesday in convoys around the city.
The protesters avoided these posts and headed toward the airport road in a procession led by a pack of hundreds of motorcycles.
Thousands of people on the backs of trucks waved flags and sang and danced to loud music that blasted through megaphones.
After the clash, soldiers took an aggressive stance, stopping and searching vehicles on the nearby Vibhavadi highway, the main gateway from the north, an area largely sympathetic to the protests.
They guarded the road into the airport and patrolled the highway on foot and on motorcycles.
For their part, the protesters turned their trucks and motorcycles around and headed back into the city, waving at the police.
Protesters in Thailand clashed today with government police, killing at least one soldier and wounding eighteen more in what media reported as being a "very tense and intense standoff."

The violence, unusually outside of the center of Bangkok, included Thai security forces firing on protesters, apparently with both rubber bullets and live ammunition, which police had been authorized to use in self-defense. The conflict took place along a highway that a convoy of protesters was travelling along; government forces were trying to disperse the demonstrators.

Casualties of the fighting included one dead — a soldier apparently killed by friendly fire — and at least eighteen injured, including eight demonstrators.  Government forces had, according to reports, fired both into the air and into the protestors from behind defenses such as razor wire and concrete pilings in an attempt to disperse the crowd.

The demonstrators have largely paralyzed the city of Bangkok for the past seven weeks in protests that have killed at least 26 people.  Largely rural and urban poor, they say they will not leave until the Thai prime minister, Abhisit Vejjajiva, resigns and new elections are held; many support former PM Thaksin Shinawatra, and consider they were deprived of their votes when he was ousted in a coup in 2006.  The fighting has led to constant rumors of a military crackdown on the city.