The video clip shows the couple in a prolonged embrace as three voices speaking in the local Shanghai dialect can be heard in the background laughing and making lewd sexual comments.

'We have wrapped up an internal investigation and found the videotape was uploaded by people who had worked for Shanghai Metro,' officials with the Shanghai Metro Operation was quoted as saying by the Xinhua news agency.

'We made formal apologies and are negotiating with the couple over compensation.'

The company found three staff members were responsible for capturing and uploading the video clip, Xinhua said, adding that one woman was fired while two had left the company last September.

The three-minute footage, titled 'Shanghai metro line staff secretly tape lovers kissing goodbye,' has attracted thousands of hits on popular sites such as Youtube and sina.comsince it was put online earlier this week, it said.

In communist China privacy was virtually non-existent in the past, when the state interfered in all aspects of people's lives.

However, a sense of privacy has emerged with economic reform and the retreat of the state apparatus from society. -- AFP