BEIJING - Police and cultural authorities have ordered museums to tighten security, following three thefts this year.

The crimes include a May raid at the Palace Museum in China's capital, in which several exhibited items on loan from a Hong Kong museum were stolen.

"People who have been lured by the high profits attained through the theft and smuggling of ancient relics tend to set their sights on museums," according to a circular jointly released on Tuesday by the Ministry of Public Security and the State Administration of Cultural Heritage.

The circular states that police and cultural authorities will carry out security checks at museums before the end of this year, suspending the operation of those with flaws.

Museums are also urged to make emergency response plans and conduct drills every six months.

Thefts from museums are rare in China. Previous incidents related to cultural relics largely involved illegal excavation of ancient tombs.

In January, three raiders overcame security guards and broke into a museum in the city of Huanggang in Hubei province. The thieves took three bronzeware items dating back to the Warring States Period (475-221 BC).

The next month, 16 cultural relics were stolen from a museum in Rugao, Jiangsu province.