Tensions are rising between Thai authorities and protesters demanding the resignation of Prime Minister Samak Sundaravej.
Thai police Friday fired tear gas to disperse some 2,000 anti-government protesters gathered outside police headquarters in Bangkok.
The demonstrators were calling on police to turn over any officers responsible for clashes earlier at the main government compound, where protesters have been consolidating
More than 10,000 activists aligned with the opposition People's Alliance for Democracy have barricaded themselves at the Government House compound since last Tuesday.
Anti-government demonstrators also have forced officials to shut down three airports in southern Thailand, including the popular resort island of Phuket.
Also, railway workers staged a work stoppage that disrupted train service nationwide.
Prime Minister Samak met with security officials Friday to discuss the situation. He said he is not declaring emergency rule, but he has not ruled out the option.
The protesters accuse Mr. Samak of being too close to former Prime Minister Thaksin Shinawatra. Mr. Thaksin was ousted in a 2006 coup and is accused of corruption.
Mr. Thaksin is in self-imposed exile in Britain. His allies, led by Mr. Samak, won parliamentary elections in December 2007.
Mr. Samak has accused the opposition of trying to trigger another military coup. But the military has said it does not plan to overthrow the government.
Some information for this report was provided by AP, AFP and Reuters.