BEIJING — A group of six Americans who were taken into custody on Tuesday as they tried to protest China’s rule in Tibet have been given 10-day detentions, the Chinese police confirmed Friday.

Extrajudicial detentions, a common punishment for Chinese dissidents, are rarely handed out to foreigners, who are often deported almost immediately after being taken into custody.

Members of Students for a Free Tibet have staged eight protests involving 55 people since the Olympics began on Aug. 8. Human rights advocates speculated that the government might be seeking to deter those contemplating similar activities in the Games’ final days.

J. Alexander Hamilton, a spokesman for the American Embassy in Beijing, said United States officials were working with Chinese authorities to gain more information about the detainees. “Our policy is to encourage the Chinese government to respect free expression and freedom of religion, which are protected by law,” he said.

Reached by phone, Public Security Bureau officials declined to comment but faxed a two-sentence statement explaining that the six Americans had been “apprehended for upsetting public order.” The statement, which did not include the detainees’ names, said the men were being held at the Dongcheng police station in Beijing.

According to Students for a Free Tibet, among those in custody are Brian Conley, 28, a video blogger from Philadelphia, and James Powderly, 31, an artist from New York who had planned to project the words “Free Tibet” on a building with laser beams. The others are Jeff Goldin, 40; Michael Liss, 35, and Tom Grant, 39, all from New York, and Jeffrey Rae, 28, from Philadelphia. Five other Americans who were detained Tuesday were deported Wednesday. They had raised a banner near National Stadium with “Free Tibet” spelled out in lights in English and Chinese.

The organization was founded in New York in 1994 and claims 650 chapters worldwide, at schools in more than 30 nations. Most of its demonstrations here have involved unfurling “Free Tibet” banners or displaying Tibetan flags, which are illegal in China.

In the latest action, just after midnight Thursday morning, four protestors raised their fists and shouted slogans while waving a Tibetan flag near National Stadium. As with the other protests, the participants were quickly bundled away by plainclothes police.

Lhadon Tethong, executive director of Students for a Free Tibet, said that German and British consular officials have told the families of the German and British detainees that they, too, would probably receive 10-day sentences.

Two photographers at the scene for The Associated Press were also roughed up and taken into custody, according to news agency reports and press freedom advocates. After the photographers were questioned separately for 30 to 40 minutes, the police confiscated the memory cards from their cameras.

In the past month, the Foreign Correspondents Club of China has received dozens of complaints from overseas journalists who were detained, trailed or had equipment damaged by the police.

“When it comes to media freedom during the Olympics, China is not even on the awards podium,” Jonathan Watts, the club’s president said.

On Friday, Students for a Free Tibet declared that its Olympics campaign had succeeded and was winding down. In characteristically stealthy fashion, the announcement was made by two members who summoned reporters to a street corner with 20 minutes notice.

The members, Alice Speller and Ginger Cassady, said that even though the protests had been fleeting and witnessed by only a few Chinese, they had helped highlight the issue in the foreign media.

“China is trying to show the world this face, that they are a modern, progressive country but that really isn’t the truth,” said Ms. Speller, a law student from Britain. “The real face is one that denies freedom of expression, and that denies it brutally and violently when it can.”

Soon after the news conference began, police officers arrived and began videotaping. But with no banners or Tibetan flags on display, the officers appeared to lose interest and drove away. The women seemed both relieved and disappointed.

Asked whether the group might be planning any more protests, Ms. Speller shook her head and said, “We’re the last two standing,” before heading down the street surrounded by a scrum of cameras.