Beijing: A fire that broke out on a foreign-flagged cargo ship undergoing maintenance at a port in eastern China on Thursday caused "heavy casualties", state media reported, as President Xi Jinping called for urgent search and rescue efforts.

The vessel, operated by Beihai Shipbuilding Co Ltd, caught fire while docked for maintenance at the port in Qingdao, Shandong province, state news agency Xinhua reported.

"A foreign cargo ship of Beihai Shipbuilding Co., Ltd. in Qingdao, Shandong Province, caught fire during its port call for maintenance, causing heavy casualties," Xinhua said.

The agency did not provide details on the number of people killed or injured, nor did it give a cause for the blaze.

Xi "stressed the need to urgently search for missing persons... and strictly hold those responsible to account", Xinhua reported.

According to state media, the fire broke out at around 11:15 am (0315 GMT). There was no immediate confirmation on whether the blaze had been brought under control.

Premier Li Qiang also called for efforts to rescue "trapped" people and ensure that those injured receive medical treatment, while urging authorities to "and strictly prevent secondary disasters".

Qingdao Beihai Shipbuilding is a major shipyard and a subsidiary of China State Shipbuilding Corporation.

Xi also warned that "all regions and relevant departments must draw profound lessons from this incident, thoroughly investigate and rectify all types of fire hazards".