China's relations with Turkey have been strained by last month's unrest in China's northwestern Xinjiang region, where clashes involving Uighurs, who are mostly Turkic-speaking Muslims, Han Chinese and government forces left around 200 people dead.

Turkish protest

At the height of the violence, Recep Tayyip Erdogan, Turkey's prime minister, called for "these incidents that have reached the level of savagery to be rapidly stopped" and said there should be an investigation.

His trade minister, Nihat Ergun, called on Turkish consumers not to buy goods from China and about 10,000 people attended an Istanbul protest against what they saw as Chinese mistreatment of Uighurs.

China issued a similar security alert to its citizens in Algeria last month following warnings that al-Qaeda could be plotting attacks on Chinese workers in North Africa to avenge the deaths of Muslims killed during the unrest in Xinjiang.

Beijing says it has brought prosperity to Xinjiang, a region that has seen annual growth rates of up to 17 per cent in recent years.

But Uighurs say the government's encouragement of mass Han Chinese emigration to Xinjiang and its policies of discrimination and repression have stoked ethnic tensions and sown seeds of violence.

Exiled Uighur activists have distanced themselves from threats of violent reprisals, saying they oppose the use of violence from any side.

"I do not believe violence is a solution to any problem," Rebiya Kadeer, the Washington-based head of the World Uighur Congress, said in response to the reported al-Qaeda threat last month.

"Global terrorists should not take advantage of the Uighur people's legitimate aspirations and the current tragedy … to commit acts of terrorism targeting Chinese diplomatic missions or civilians."