In updated travel advice, the State Department warned that political demonstrations were expected to continue "indefinitely" in Bangkok and that they could suddenly escalate into violence.

"US citizens are urged to avoid the areas that may be targeted for demonstrations and to exercise caution in their movements around Bangkok," the State Department said.

However, the State Department said that incidents in Thailand "appear to be motivated by domestic politics and do not appear to be acts of international terrorism."

"Travel to Thailand remains generally safe," it said.

The travel advice is similar to guidance given to US citizens a week ago except the updated statement does not specifically ask travelers to avoid Khao San Road, a backpacker haven where the protests spilled over.

The travel alert was issued as Thailand toughened its stance against protesters, warning that security forces would use live ammunition and tear gas in any fresh clashes.

The anti-government demonstrators, known as Red Shirts, canceled a rally in the financial hub.

Meanwhile, the Tourism Authority of Thailand (TAT) advised visitors to avoid the following areas commonly used foropposition rallies:

• Ratchaprasong intersection
• Rama I Road Outbound from Chaloem Phao intersection where Henri Dunant Road meets Rama I Road to Ratchaprasong intersection
• Rama I Road Outbound from Ratchaprasong intersection to Pratunam intersection
• Ploenchit Road Inbound from Chidlom intersection to Ratchaprasong intersection
• Victory monument (daily from 3pm - 6 pm)

The TAT also said that security has also been tightened at major transport hubs and public buses had been told to change their usual routes, if necessary, and alternate routes will be available if the main routes should be blocked by the red-shirts rallies