Chinese authorities have barred the British finance director of GlaxoSmithKline (GSK) in China from leaving the country, the company said Thursday as it faces a bribery probe.

But the Shanghai-based executive, Steve Nechelput, has not been detained or arrested, GSK said.

"We have been aware of travel restrictions for Steve since the end of June. His travel is unrestricted within China," it said in a statement to AFP.

A spokesman for the British Consulate in Shanghai said it was providing him assistance, but declined to go into details.

Chinese authorities allege GSK staff bribed government officials, pharmaceutical industry groups, hospitals and doctors to promote sales.

Police have already detained four top executives of GSK, all Chinese nationals, a ministry of public security official said earlier this week.

Media reports say more than 20 people have been detained in the case, including pharmaceutical and travel industry personnel.

GSK employees gave the bribes directly and through travel agencies and project sponsorship, the public security ministry said last week.

GSK executives also took kickbacks from travel agencies in return for organising conferences, some of which did not exist, according to an interview with one of the detained executives aired on state television.

Chinese state media on Wednesday blasted GSK for being "dirty and devious", accused the firm of inflating its prices and said the case provided a lesson for others.

GSK has said it "shares the desire of the Chinese authorities to root out corruption" and would "cooperate fully" with the investigation.

"These allegations are shameful and we regret this has occurred," it said in a statement earlier this week.