China tomb raid
Workers rest near a pit dug to investigate suspected imperial era tombs in Beijing.Reuters

Chinese authorities have detained more than 120 alleged tomb raiders in a massive police operation.

The arrests were made in connection with 144 break-ins that saw hundreds of valuable artefacts looted from ancient grave sites in Shaoxing, Zhejiang province, police said.

1,335 relics were seized during the operation, with more than 800 police officers involved in the investigation. A total of 124 alleged perpetrators are currently being held by police.

The prefecture of Shaoxing, south of Shanghai is home to hundreds of historic graves, some dating back more than 1,500 years.

Local authorities described the tomb raiding case as the "biggest ever" in Zhejiang's history, the South China Morning Post reported.

Archaeology experts were analysing the recovered artefacts, looking for "pieces of national heritage", a detective told the Qianjiang Evening News.

Among the relics found in the hands of the arrested tomb raiders was a large bronze Jin Dynasty mirror said to be more than 1,800-years-old.

Police said that most of the alleged thieves were locals, who exploited their knowledge of the area and its history to carry out raids.

"They tend to have a good understanding of the history of Shaoxing, they know where to find the tombs," a Shaoxing municipal public security bureau officer said.

Illegal tomb excavations are an endemic problem in China, with reports of hundreds of thousands of people involved in the crime.