BEIJING - Two Americans and two British nationals have been ordered to leave China "within a prescribed time limit" after displaying "Free Tibet" banners near an Olympic venue in Beijing on Wednesday, local police said.

Two are expected to leave on Wednesday night and the other two on Thursday.

"They disrupted public order and violated Chinese laws. Their period of stay in the country will hereby be cut short according to the Law of the People's Republic of China on Control of the Entry and Exit of Aliens," the Beijing Municipal Public Security Bureau said in a statement issued late on Wednesday.

The four, three men and one woman, had entered China on tourist visas.

They gathered at about 5:47 am at the Beichen Overpass near the National Stadium, or Bird's Nest, in Chaoyang District in northeast Beijing.

Two of the men climbed up two electricity poles and hung the banners.

One banner bore large black letters declaring "One World One Dream Free Tibet," while the other said: "Tibet will be free" in English and "Free Tibet" in Chinese.

Local police rushed to the scene 12 minutes later and took them away.

Sun Weide, a media official of the Beijing Organizing Committee of the 29th Olympic Games, expressed strong disapproval of their behavior.

"We resolutely oppose such behavior," Sun said. The Olympics was a grand international sports gathering, he said, and "we are resolutely against any attempts to politicize the Games."

"China has stipulated laws and regulations concerning gatherings and demonstrations. We hope foreigners who come to China can observe China's laws and regulations," he said.

Also, on Wednesday afternoon, three American nationals staged a sit-in and shouted anti-abortion slogans outside the National Museum of China, east of Tian'anmen Square in downtown Beijing.

The three, two men and one woman, were persuaded by police to leave about 30 minutes later.