A police officer was stabbed to death in the street over a row about watermelons.
Three men have been arrested for on suspicion of murdering the city management officer in Lanzhou city, capital of north-western China's Gansu province.
Footage filmed at the scene of the incident shows one man covered in blood lying motionless on the ground.
Officers working for parallel police force the Urban Administrative and Law Enforcement Bureau - 'chengguan' for short - were attempting to stop a melon farmer and his two sons from selling watermelons by the roadside, according to reports.
Their business had been deemed illegal or without permit and officers were seeking to confiscate their goods and seize their vehicles.