A high-profile tomb robbery case was closed at the end of last year, with 30 defendants given sentences ranging from three years to life imprisonment, a court in Liaoning province said on Monday.

The Chaoyang Intermediate People's Court announced the judgment on Thursday in which five defendants, including the ring leader surnamed Yao, were sentenced to life in prison for stealing cultural relics from the Hongshan cultural relic protection region.

The other 25 defendants received sentences ranging from three to 15 years in jail on the same charge, the judgment said.

Of the defendants, four were archaeologists.

A total of 280 stolen relics, including 29 classified as national level, have been recovered, the court said.

The case was said to be the largest example of cultural plunder since the founding of the People's Republic of China in 1949. The number of cultural relics and the number of people involved in the thefts both set records, according to the court.

The police in Chaoyang found several clues pointing to illegal excavation and set up a special investigative team.

In December 2014, 785 police officers who were sent to 10 cities in seven provinces, including Liaoning, Henan and Shaanxi, moved against 10 gangs suspected of robbing graves and detaining all the suspects who were later convicted.

In the Hongshan cultural relic protection region, located along the border of Lingyuan and Jianping counties, five key historical finds have been unearthed, including a large altar thought to be 5,500 years old. The region is home to a number of other cultural relics, according to the court.

The region, created in 1921, is a key national relics site and was a candidate for UNESCO World Cultural Heritage designation in 2013, the statement said.

Chen Zhijun, a criminal law professor at People's Public Security University of China, applauded the judgment, saying that such large-scale tomb robbery has been rare since the 1980s.

"There were a series of crackdowns, and relics theft was added to the Criminal Law. In the 1990s, a law was drafted to protect relics, which contributed a lot to reducing and fighting theft," Chen said.

Although the death penalty for the crime was revoked in 2012, "the fight and efforts to protect cultural relics was not weakened", he said.

Zhao Li, a criminal lawyer in Beijing, said the life imprisonment sentences given to five convicts in the case showed the seriousness of their behaviors. "After all, robbing a grave isn't like stealing other property," Zhao said, "because some relics cannot be repaired after they are damaged, and some are priceless."