TAIYUAN, Oct. 8 (Xinhua) -- Police in north China's Shanxi Province have seized over 5,000 historical artifacts and arrested hundreds in a large-scale operation against tomb raiding and relic smuggling this year.

The operation, beginning in March, has been the province's largest police operation of its kind. The police campaign has helped retrieve 5,730 historical artifacts, among which 33 are on the list of China's national-level cultural protection.

Both the number of suspects and the retrieved relics surpassed the total numbers between 2013 and 2017, according to the Shanxi provincial bureau of public security.

"During the operation, police spared no efforts to track down the stolen relics," said Liu Xinyun, deputy governor of Shanxi and the provincial police chief.

Tomb raiding has been a serious problem in Shanxi, which is home to 452 cultural relics sites under state-level protection and more than 28,000 ancient architectural sites -- the highest of all provincial regions.

A set of bronze bells dating back to the Shang Dynasty (around 1600 BC - 1046 BC) had been smuggled and traded several times before police traced them back from a Hong Kong antique trader during their investigation.

Police said once the relics were smuggled abroad, it would become difficult to retrieve them, even after the smuggling was uncovered.

Wang Jingyan, a researcher with the Shanxi provincial archaeological institute, said that at an important cultural site in Xiangfen County, where a complex of tombs dating from the Western Zhou Dynasty (1046 BC - 771 BC) to the Warring States Period (475 BC - 221 BC), nearly half of the 250 tombs had been robbed before an official excavation was made.

"The tombs were mostly robbed and consequently damaged in 2013. It was heartbreaking for archeologists," Wang said, adding that the provincial archaeological institute carried out an emergency rescue excavation to protect the remaining tombs in 2014.

The provincial museum held a three-month exhibition featuring 4,431 of the recovered cultural relics, mostly bronzeware from the Shang and Zhou dynasties. The exhibition was closed in late August.

During the police operation, a total of 543 suspects have been arrested, and a number of tomb-raiding gangs were busted.

Among them, a key member of a tomb-raiding gang was sentenced to death with a two-year reprieve, and four other principal members were given life imprisonment. In addition to tomb raiding and relic smuggling, the gang was also involved in mafia-style criminal activities of drug trading and gambling.

Two former deputy police chiefs in Wenxi County, Yuncheng, were given life imprisonment in the same case, for offering a "protective umbrella" for the gang's illegal business.