CHITA, August 4 (RIA Novosti) - Russia has tightened security on part of the border with China due to an outbreak of pneumonic plague in the Qinghai province.

The town of Ziketan in northwest Qinghai was quarantined after the outbreak was registered on July 30. Twelve people have been infected, of whom three have died.

A spokesperson for the customs service in the Transbaikal area, to the east of Siberia's Lake Baikal, told RIA Novosti that no signs of infection have so far been detected near the border.

Russia's chief sanitary official Gennady Onishchenko advised Russians on Tuesday to avoid travelling to China's "problem regions."

The head of the local department of national consumer rights regulator Ropotrebnadzor told RIA Novosti that Transbaikal has historically been a plague hot spot, due to its proximity with China and Mongolia.

"A lot depends on the number of wild rodents, who are the main carriers of the fleas that spread the plague. We have an anti-plague station operating in the region, which is studying these processes," Vladimir Pintusov said.

According to the World Health Organization, pneumonic plague, which affects the lungs and can be transmitted from person to person or from animals to people, can be fatal within 24 hours of infection.