Friction on the dance floor, rather than racism, is behind a physical conflict outside a bar in downtown Shanghai last week in which a French man suffered a head injury and bruises, police said on Tuesday.

In a telephone interview, a spokesman for the Shanghai Public Security Bureau said that four Chinese men have been detained in the alleged attack on the French man, identified only as Thomas, on the morning of June 10 outside the Shanghai bar No 88. Police are still searching for a fifth suspect.

"It's just a civil case caused by a dispute on the dance floor," the spokesman said. "It has nothing to do with racism or the recent attack of Chinese students in southwestern France."