Japan urged its nationals to avoid wearing red or yellow colors in Bangkok, while France and Britain advised citizens to stay indoors as rioting spread Monday in the Thai capital and countries worldwide issued travel advisories.

Americans were urged to "exercise caution" in Bangkok and South Korea called on its citizens in the Thai capital "to return home (to Korea) if they are not on urgent matters".

A violent showdown between soldiers and anti-government protesters flared in more than a dozen parts of Bangkok, as protesters burned public buses and set tires on fire that sent plumes of black smoke into the sky.

The protesters are demanding the resignation of Prime Minister Abhisit Vejjajiva. On Sunday, a group of protesters viciously attacked Abhisit's car by hurling chunks of concrete and metal barricades at his armored vehicle, before he was able to escape. They wear red to distinguish themselves from rival protesters, who dress in yellow.

"We recommend you should avoid wearing red or yellow shirts," Japan's Foreign Ministry urged citizens in a statement.

The US Embassy issued a message urging Americans "to avoid the areas of demonstrations and to exercise caution anywhere in Bangkok".

Australia advised its nationals to reconsider traveling to Bangkok or surrounding provinces, and to "exercise a high degree of caution because of the political instability in Thailand and the possibility of political demonstrations."

"The French Embassy strongly recommends that French nationals stay in their homes or hotels," said a statement on the embassy's website that also recommended postponing nonessential travel until calm returns.

Thailand's government spokesman Panitan Wattanayagorn repeatedly appeared on national television Monday, at times speaking in English, with updates on the security situation.

"We must protect foreign tourists," the government spokesman said, urging Thais to help keep foreigners up to date on the crisis as some areas cleared of clashes and new ones arose. "If you have foreign friends, please help them."

The rioting comes just months after a rival group of yellow-shirted protesters shut down Bangkok's two airports during a weeklong shutdown that stranded more than 300,000 travelers.

Hundreds of local and foreign tourists still gathered Monday to celebrate the water festival in Bangkok's Khao San Road, a magnet for budget travelers, but some businessmen wondered how many foreigners would be back next year.

"This could be the last time you see such joy and celebration here in Thailand," said a less-than-festive Surat Wongcharnsilp, chairman of the Association of Khao San Business Operators.

"Around 80 percent of tourists have checked out and more tourists are expected to leave after Songkran," Surat said, referring to the water festival that marks the start of the Thai New Year.

In 2007, 14.5 million foreigners visited Thailand. Official full-year data was not available for 2008, but in the first 11 months, arrivals touched 13.2 million.

Apichart Sankary, president of the Association of Thai Travel Agents, was quoted in the Bangkok Post as saying on Sunday that tourist arrivals could fall below 10 million this year.

"Right now, there's no hope for the Thai tourist industry," Surat said.

(China Daily April 14, 2009)