Hundreds of Thai riot police have confronted anti-government protesters at a barricade in Bangkok's business district, but have since pulled back without violence.
The tense scenes on Friday come a day after grenade attacks in the area killed three people in the country's capital and wounded at least 75.
Thai television says police went right up to the barrier and demanded the red shirt protesters dismantle it, but they made no move to do so.
A photographer for Reuters says protesters poured fuel onto the barricade, made up largely of tyres. The photographer says police later pulled back, and the protesters have retreated to a camp they have set up behind the barrier.
The government said the grenades on Thursday were fired from the red shirt protest area. Leaders of the red shirts, who have been demonstrating in Bangkok for six weeks seeking new elections, denied they were to blame.
The grenade blasts came after clashes between troops and protesters killed 25 people and wounded more than 800 on 10 April in Thailand's worst street violence in 18 years.
The central bank said on Wednesday that the political crisis was affecting confidence, tourism, private consumption and investment, although exports, which are crucial to economic growth, have been little affected by the unrest.
Prime Minister Abhisit Vejjajiva has called an emergency meeting with security chiefs.