U.S. President George W. Bush added his voice Wednesday to a growing international chorus of concern about the crackdown on pro-independence protesters in Tibet.

Bush called Chinese President Hu Jintao on the telephone and "raised his concerns about the situation in Tibet," said White House spokeswoman Dana Perino.

"[He] encouraged the Chinese government to engage in substantive dialogue with the Dalai Lama's representatives and to allow access for journalists and diplomats [to Tibet]."

It's the strongest direct expression of concern so far by the U.S. over China's reaction to protests in Tibet and neighbouring provinces. 

Bush's call to Hu came as China allowed a small number of foreign journalists into the Tibetan capital, Lhasa, for the first time since violence broke out in the disputed region earlier this month.

Chinese paramilitary police officers patrol inside the Gongkar airport in Lhasa, China. The first group of foreign journalists allowed into Tibet since anti-government riots broke out arrived in Lhasa on Wednesday. (Andy Wong/Associated Press)

A bus drove the reporters through several police checkpoints, passing police officers posted at almost every cross street along the way to Lhasa, where several days of peaceful demonstrations turned violent on March 14. Police with machine guns appeared to be posted at government offices.

The reporters were part of a Chinese-government-arranged, two-day visit.

An officer told reporters they were checking vehicles for seat belt and licence violations.

Reporters were shown buildings torched in the violence in Lhasa, as well as intact buildings draped with white fabric. Many Tibetans used the fabric during the rioting as a way of signalling protesters to not stone or burn the buildings because they belonged to Tibetans.

The police presence in the parts of the city where reporters were taken was not noticeably heavy. In the Old City, members of the People's Armed Police were checking identification but allowing people to pass by.

The reporters were not prevented from leaving their hotel Wednesday night but were encouraged not to go out by their government handlers.

Protesters turned themselves in, media claim

Also Wednesday, Chinese state-run media reported more than 600 people had turned themselves in to police in Lhasa and in Sichuan province, where violent protests had spread.

Police have also published a list of dozens of people wanted in connection with the violence.

The demonstrations have spread to other ethnic Tibetan regions of China, including a protest Wednesday in the western province of Qinghai. In that protest, police clamped down on dozens of pro-Tibetan marchers, who then staged a sit-in. The demonstrators were dispersed, said Reuters news agency.

China's tight control of the media makes it difficult to know how many people have been killed or injured in the weeks of violence. The government says at least 22 people have died in Lhasa; Tibetan-rights groups say nearly 140 Tibetans were killed, including 19 in the northwest province of Gansu.

The uprising is the broadest and most sustained against Chinese rule in almost two decades, embarrassing and frustrating the Communist leadership. Thousands of troops and police have been deployed to contain the unrest.

Calls for boycott

China's handling of unrest in Tibet has drawn criticism and calls from pro-Tibet groups to boycott the upcoming summer Olympic Games in Beijing.

While the U.S., Britain and Germany have stopped short of threatening to boycott the Games, some European leaders suggested they wouldn't rule it out.

French President Nicolas Sarkozy said Tuesday he would consider boycotting the Aug. 8 opening ceremony.

The head of the European Parliament invited the Dalai Lama, Tibet's spiritual leader in exile, to address the European Union and questioned whether European leaders should attend the opening of the Games.

"I genuinely say that all politicians must ask themselves whether they can attend the opening ceremony if China fails to take part in dialogue," Hans-Gert Poettering said during an emergency debate on Tibet.

Some members of the Parliament wore t-shirts depicting the five Olympic rings shaped as handcuffs while others draped Tibetan flags over their seats.

Belgian Vice-Premier Didier Reynders suggested an Olympic boycott would not be ruled out, telling Le Soir newspaper on Wednesday "we can never exclude" the option.

The White House said earlier that President Bush would be attending the Games because he believed them to be about sport, rather than politics.

with files from the Associated Press