BEIJING - Chinese archaeologists have found an ancient sunken ship in the South China Sea laden with Ming Dynasty porcelain, the Xinhua news agency said on Wednesday.

Divers used satellite navigation equipment to find the vessel, dubbed South China Sea II, which is about 17 to 18 metres (yards) long and lying at a depth of 20 metres.

"A preliminary study of the sunken ship shows it may have sunk 400 years ago after striking a reef," archaeologist Dr Wei Jun was quoted as saying.

The ship came to light when local police got wind of illegal salvage operations going on off the coast of Guangdong province.

"On May 25, police learnt that some fishermen had been recovering ancient porcelain objects from the sea," Xinhua said.

Police confiscated 21 pieces of porcelain from a fishing boat whose owner claimed that divers he had hired for deep-sea fishing had recovered the porcelain by accident.

On May 26, another 117 pieces of porcelain were confiscated from two fishing boats carrying out illegal salvage work.

"Police stepped up monitoring of the area and warned local people not to loot the cultural relics. On June 1, two local residents handed over 124 porcelain items to police."

The sunken ship was found just a few days after China began salvage operations at another wreck site dating back to the days of the Song emperors, who ruled between AD 960 and 1279.

South China Sea I, discovered in 1987, was the first ancient vessel discovered in the area along the "Marine Silk Road" linking imperial China with the West.

"The discovery of South China Sea II will provide more evidence about the Marine Silk Road, and help with the study of Chinese seafaring, shipbuilding and ceramics making," Wei said.

Foreign smugglers were using advanced technology to steal China's seabed treasures, mostly porcelain from ancient shipwrecks. Many relics were being shipped to the United States and other antique markets.

Art collectors and dealers have been pursuing China's seabed heritage in earnest since early 2005, when about 15,000 pieces, mainly blue-and-white porcelain about 300 years old, were found in a shipwreck off the southeastern province of Fujian.