(Adds background, detail, byline)

By John Ruwitch

SYDNEY, Sept 7 (Reuters) - U.S. President George W. Bush on Friday demanded the immediate release of Myanmar activists detained by the army and called on the ruling junta to stop "assaulting pro-democracy activists".

The comments come a day after hundreds of Buddhist monks held a group of government officials for several hours and torched their cars in anger against the military that rules the impoverished Southeast Asian country, formerly called Burma.

"We must press the regime in Burma to stop arresting, harassing, and assaulting pro-democracy activists for organising or participating in peaceful demonstrations," said Bush in a speech to Asia-Pacific business executives in Sydney.

"The Burmese regime must release these activists immediately, stop its intimidation of those Burmese citizens who are promoting democracy and human rights, and release all political prisoners, including Aung San Suu Kyi," said Bush.

Nobel peace laureate Aung San Suu Kyi's National League for Democracy party won a 1990 election, but the junta has refused to be dislodged, and Suu Kyi has been under house arrest since 2003.

More than 150 people have been arrested since Aug. 19, when activists began protests against an increase in fuel prices that nearly froze transport.

Myanmar's military has ruled for the past 45 years and has been accused of human rights abuses.

But the latest crackdown has been one of the harshest since the army crushed a nationwide uprising of monks, students and government workers in 1988, when around 3,000 people are thought to have been killed.

The United States has labelled Myanmar an "outpost of tyranny" and imposed economic sanctions, but the junta has avoided total isolation by using its vast natural gas reserves to befriend energy-hungry China and India.

Washington has stepped up its criticism of the junta.

U.S. first lady Laura Bush took the unusual step of wading into international diplomacy on Wednesday when she called for the United Nations to step up pressure on Myanmar over human rights, adding she hoped China would join in.

In January, China and Russia, both APEC members, vetoed a U.N. Security Council resolution calling for Myanmar to stop persecuting minority and opposition groups and take concrete steps toward democracy.

More than 25 celebrities including actors Dustin Hoffman and Robin Williams on Thursday urged the United Nations to help win freedom for Suu Kyi, calling her "Burma's Nelson Mandela", referring to the former South African president who was jailed for his anti-apartheid stance. (Additional reporting by Matt Spetalnick in Sydney)

AlertNet news is provided by