A large crowd gathered in downtown Seoul, shouting: "Bring back alive Shin Hyo-sun and Shim Mi-son." The two 13-year-old girls were on their way to a friend's birthday party when they were run over and killed in June.

Organizers said about 300,000 people joined the protests in South Korea.

After a two-hour rally in Seoul, protesters with candles marched and sang the popular Korean folk song "Arirang." Police stopped them a block away from the U.S. embassy. Some protesters tore apart four large U.S. flags.

In Daegu, a city 200 miles southeast of Seoul, two students broke into a U.S. military base and climbed onto a 100-foot-high water tank.

Television footage showed the students, draped in South Korean flags, shouting: "Retry them in our court." They were arrested by South Korean police two hours later, all-news cable network YTN said.

Protesters in Seoul clapped and roared when speakers demanded a retrial of the soldiers in a South Korean court, and a revision of an agreement with Washington in order to give South Korea more jurisdiction over the over the 37,000 U.S. troops stationed here.

Protesters denounced the South Korean president, Kim Dae-jung, for "groveling" to the United States and called him a U.S. "puppet."

Student radicals among the crowd demanded the outright withdrawal of all US troops.

Some of the protesters, their ranks swelled by university  students on semester break, carried placards calling on the  United States to sign a non-aggression pact with North Korea.