Thousands of Thai police Saturday surrounded and cordoned off Bangkok's main airport after scuffles with protesters, raising fears that days of crippling demonstrations could end violently. Meanwhile, protesters seized a police officer, escalating tensions in a four-day standoff Saturday. The trouble started after about 1,000 demonstrators moved in on a police checkpoint near the Suvarnabhumi international airport, triggering a showdown that ended without violence when officers hastily withdrew. Police, many in full riot gear, had a much more visible presence Saturday with several hundred in the area. Associated Press reporters saw one policeman being grabbed at the checkpoint by three protesters, forcibly put in a vehicle, and driven away toward the airport controlled by the demonstrators. It was not immediately known if the officer was still being held. Frustrated tourists struggled to escape Thailand through a Vietnam War-era naval base as airport authorities announced the besieged Suvarnabhumi international airport would remain closed for at least two more days. Premier Somchai Wongsawat warned that the protests against his administration risked casting Thailand into international isolation. “To lay siege to the airports is extremely dangerous. It will make foreign countries lose confidence in Thailand.