"President Bush, who has visited Korea and has a special feeling for the Korean people, has been touched by this tragedy," US ambassador Thomas Hubbard told a press conference.

"Just this morning, the president sent me a message asking me to convey his apologies to the families of the girls, to the government of the Republic of Korea and to the people of Korea.

"He asked me to express, and here I quote, his 'sadness and regret' over this tragic incident and to reiterate the United States' commitment to work closely with the Republic of Korea to help prevent such accidents from occurring in the future."

Activists have staged regular protests outside US military installations since the deaths of 14-year-olds Shim Mi-Son and Shin Hyon-Sun on June 13, burning American flags and scuffling with riot police.

Unrest escalated after two soldiers accused of crushing the girls under the tracks of a 50-tonne military vehicle were cleared of negligent homicide by a US military court last week.

The South Korea media said the trials were a sham and mainstream political leaders joined the radical left in calling for a revision of the status of the 37,000 US troops stationed in South Korea under a mutual defense pact dating back to the 1950-1953 Korean War.

Hundreds of demonstrators rallied daily during the court martials last week outside Camp Casey, a sprawling US military post near the border with North Korea demanding that the soldiers be put on trial by a South Korean court.

But under an accord between Washington and Seoul, US forces have legal jurisdiction over American troops committing crimes in South Korea while on duty. The South Korean government asked for jurisdiction in this case but was denied.

Many Koreans are genuinely bewildered that the soldiers walked free and that no one has been held legally responsible for the killings. Under the Korean criminal justice system they would almost certainly have been jailed.

General Leon LaPorte, commander of US forces in South Korea, said the accident served to underline differences in legal systems.

"That does not mean no one is responsible and we accept full responsibility for this tragic accident," he said at the press conference with Hubbard.

Following the acquittals, protestors firebombed a US military warehouse in Seoul on Monday and dozens of activists broke into the headquarters of the 2nd Infantry Division in Uijongbu north of Seoul on Tuesday.

South Korean President Kim Dae-Jung intervened to attempt to quell mounting anti-Americanism.

"The government must sternly deal with illegal and violent demonstrations," said Kim on Tuesday.

For security reasons soldiers in areas controlled by 2nd Infantry Division, the core element of the US military presences in South Korea, were put under indefinite curfew from Tuesday.

It was unclear what effect the Bush apology would have on anti-US protests unfolding here. Some 1,000 students were gathering outside the main US military installation in Seoul as ambassador Hubbard was announcing the apology.

Earlier Wednesday the two acquitted soldiers also issued public apologies. Sergeant Fernando Nino offered his "deepest and most heartfelt condolences" to the families of the girls.

"I am so sorry for the grief and pain you have felt at the loss of your daughters," Nino, the vehicle's navigator and commander, said in a statement.

The second soldier, Sergeant Mark Walker, also expressed "great remorse" over the deaths.

"I know my mental turmoil is surely nothing compared to your sadness and pain. In my year here in Korea I have really come to love and respect the Korean people," said Walker, who was at the wheel of the tank track vehicle that ran over the girls as they walked past a military convoy on their way to a birthday party.

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