PHNOM PENH, Dec. 17-- Some 150 Buddhist monks held a protest in the capital on Tuesday morning, calling for the Cambodian government to take an urgent action against the theft of the country's only relics of the Buddha.

Monk-protesters carrying national and religious flags and banners read: "The demonstration is to demand the government to take an urgent measure for the loss of the relics of the Buddha."

"We urge the government to launch a serious probe into the loss of the relics of the Buddha last week," Venerable But Buntenh, a representative of the protesting monks, told reporters during the protest on a street in front of the Chak Tomuk Theater.

A golden urn containing what are believed to be relics of the Buddha including hair, teeth and bones was stolen from a mountaintop shrine in the former royal city of Udong in Kandal province on Tuesday last week, Kheng Tito, spokesman for the National Military Police, said.

On Sunday, the Kandal Provincial Court charged five persons with aggravated theft for their suspected involvement in stealing the relics of the Buddha. So far, the whereabouts of the relics remains unknown.

The protest ended in the same morning after Venerable Khim Sorn, chief of the secretariat of the Mohanikaya Buddhist order, met with protesting monks and promised to write a letter to the government to demand the expedition of the investigation into the case.

Cambodia's late King Norodom Sihanouk brought the relics from Sri Lanka to Cambodia in the 1957 to mark the 2,500th anniversary of Buddha's birth.

Deputy Prime Minister and Cabinet Minister Sok An said Monday that an investigation into this case was underway.

"Now, all the competent authorities are working very actively on this case and when the work is in the process, I don't want to make any comments," he told reporters.

Cambodia is a Buddhist-dominant country, where about 90 percent of the 14.8 million populations are Buddhists.

Late King Norodom Sihanouk moved the relics in 2002 from the capital Phnom Penh to Udong Mountain, some 45 km northwest of Phnom Penh in an elaborate ceremony, which was attended by tens of thousands of Buddhist holders.