By BO-MI LIM, Associated Press Writer 23

SEOUL, South Korea - Police arrested 10 anti-U.S. protesters Monday and released 27 others after violent demonstrations against plans to expand an American military base, officials said.

The government vowed stern measures against future violent protests, threatening military trials for civilians who trespass on a U.S. base in Pyeongtaek, about 40 miles south of Seoul, or assault soldiers guarding the area.

The demonstrations Thursday and Friday saw protesters battling police with bamboo sticks and authorities responding with batons to evict them from the site.

The violence injured more than 200 protesters, police and soldiers.

Prosecutors secured arrest warrants for 10 of 37 protesters detained Thursday, and released the other 27 after the Suwon District Court’s Pyeongtaek division declined to issue warrants for them, the court said.

The prosecution was awaiting word from the court on whether they can press charges against 23 other protesters detained Friday and seek the re-arrest of the demonstrators who were released, prosecution spokesman Kang Chan-woo said.

For months, villagers and anti-American activists have impeded work to expand Camp Humphreys in Pyeongtaek under a 2004 agreement between Seoul and Washington to move the American military command there from its current headquarters in central Seoul.

Several villages on the outskirts of Pyeongtaek, a city of 360,000 people, must be razed for the base construction.

The government has offered residents financial compensation to move out, but some 70 households continue to resist, according to the Defense Ministry.

On Thursday, authorities sent more than 10,000 riot police to the site, evicting protesters and destroying an abandoned school used as a base for the protesters. Army engineers also set up wire fences around the site to keep outsiders away.

But activists returned Friday to stage more protests. TV video showed stick-brandishing demonstrators cutting wire fences and beating unarmed troops guarding the site.

On Monday, Defense Minister Yoon Kwang-ung said people who attack soldiers or destroy military properties pose a "direct challenge to public authority."

"We will apply related military laws accordingly in the future in keeping with law and principle," Yoon told South Korean reporters in comments confirmed by his ministry.

South Korean law allows civilians to be tried in the military court when they are accused of assaulting guards on duty or trespassing on military property.

About 29,500 U.S. troops are stationed in South Korea as a legacy of the 1950-53 Korean War, which ended in a cease-fire instead of a peace treaty, leaving South Korea still technically at war with the communist North.

The number of troops is set to decline to 25,000 by 2008 as part of the Pentagon’s worldwide realignment of its forces.