BEIJING -- China's Ministry of Culture is to launch a probe into Icelandic singer Bjork's declaration of support for Tibetan independence during a March 2 concert in Shanghai.

It also pledged to tighten scrutiny of artists to make sure there is no repeat performance.

"Any attempt to separate Tibet from China will definitely be opposed by the Chinese people and all righteous men across the world," the ministry said on its website on Friday.

Bjork's protest was a reminder of how tough it will be for the Chinese government to keep a lid on politically uncomfortable remarks at August's Olympic Games in Beijing.

Her Shanghai surprise came as Tibetan independence groups are running high-profile campaigns ahead of the Games.

"We will further tighten controls on foreign artists performing in China in order to prevent similar cases from happening in the future," the ministry warned.

Bjork uses the song "Declare Independence" to highlight political issues. At the end of her performance of the song, which the ministry described as "unapproved," Bjork sang "Tibet, Tibet."

Her "political show has not only broken Chinese laws and regulations and hurt the feeling of Chinese people, but also went against the professional code of an artist," the ministry said.

Bjork is the latest of a host of warblers to play in China. Until a couple of years ago only the safest pop was allowed, such as Elton John and Wham!

More risque acts have come to China lately but bands like The Rolling Stones have stuck closely to the agreed text to avoid offending their hosts.

The People's Liberation Army occupied Tibet in 1950 and Beijing has since kept a tight grip on it.

Beijing says it is bringing economic prosperity to the desperately poor region and that Tibetans enjoy a high degree of autonomy.

Hollywood stars such as Richard Gere and pop stars such as The Beastie Boys have taken high-profile stances backing the Dalai Lama, who fled Tibet in 1959 after a failed uprising.