China's Ministry of State Security warned holiday travelers on Sunday against illegally bringing foreign pets, plant seeds and human genetic samples across the border, warning that biosecurity risks pose a direct threat to national security.

The statement by the ministry comes during the peak of the National Day travel rush, when tens of millions of Chinese travelers go abroad or return home.

The ministry said China imposes quarantine, inspection and supervision on all animals, plants and their products entering or leaving the country. But some people have tried to sneak such items across the border through concealment, false declaration and other illegal means.

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Exotic animals are among the commonly seized unauthorized items, the ministry said. Last year, Chinese customs authorities intercepted 5,439 batches of alien species through inbound baggage, mail and other channels.

In the first quarter of this year, customs seized more than 1,000 exotic animals, including arthropods such as beetles and spiders, amphibians such as frogs and salamanders, and reptiles such as lizards and snakes.

"The entry and exit of such live animals and specimens requires complete quarantine and approval procedures," the ministry said in a statement.

In addition to exotic animals, the import and export of plant seeds and seedlings are also under strict supervision.

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Some people view buying novel flower and grass seeds from abroad to grow at home as a purely personal hobby, while others take distinctive domestic seedlings and seeds abroad to give as gifts. Such acts pose national security risks, the ministry said.

In one case in May, customs authorities intercepted 50 packets of mixed seeds, each weighing 500 grams and containing large quantities of cannabis seeds. They were found in mail declared as personal items.

With genetic technology developing rapidly, the ministry said certain foreign organizations have entered ecologically sensitive areas in China under the guise of tourism or scientific research, or illegally collected human blood samples in the name of medical testing, in an attempt to steal China's genetic resources and research data.

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Last year, customs in Guangzhou, Guangdong province, busted a series of cases involving the smuggling of pregnant women's blood samples, cutting off a cross-border black-market chain affecting 23 provinces.

The ministry stressed that illegally bringing alien species into China or smuggling native organisms and genetic resources overseas can harm the ecological environment, agricultural production, public health and biosafety.

It reminded travelers not to carry animals, plants, seeds or other such items without authorization when traveling abroad, or bring back biological materials when entering China.

Those who need to import or export biological materials for research, teaching or other purposes should apply in advance for permits from relevant government departments, declare them truthfully and submit them to quarantine. Smuggling biological materials is illegal, and violators face criminal prosecution, the ministry warned.

Anyone who discovers suspicious clues involving the illegal entry or exit of biological materials should promptly report them to the relevant authorities and assist in the investigation, the ministry added.