Chinese officials have sprayed almost 200 acres of land with poison as part of a rat and flea eradication campaign after a case of bubonic plague was reported in a northern region.

The Ulanqab government in central Inner Mongolia said it carried the spraying last week, while another local authority posted images of cadres dressed in white scrubs and and said they dispatched planes to spray poison as part of "rat- and flea-extermination work".

The germ Yersinia pestis can be transmitted to humans from infected rats via fleas and the reported case has spurred efforts across the region to kill pests.

Earlier this month two patients from the same region were diagnosed with the highly-contagious pneumonic strain of the plague and moved to Beijing for treatment.

The pneumonic strain an prove fatal in 24 to 72 hours and is the "most virulent form" of the disease according to the World Health Organisation (WHO), while the bubonic form is less dangerous.

"We will do our best to prevent and control, block and annihilate, and take strict precautions against the outbreak and spread of the epidemic," said the Xianghuang Banner government.

Meanwhile, those who have had "close contact" with the three plague patients have undergone quarantine and medical observation, according to the Beijing and Inner Mongolia commissions.

Currently, the two patients in Beijing are "critically ill", said the Beijing Municipal Health Commission last week, while the third person, who is being treated in Ulanqab, is in "stable" condition.

Though the highly-contagious plague is rare in China, several cases have proven deadly in the past few years.

According to China's National Health Commission, a total of five people have died from the plague between 2014 and September of this year.

In 2014, a man died of the plague in northwestern Gansu province and sparked the quarantine of 151 people.

The 30,000 people living in Yumen, the town where the man died, were also prevented from leaving, with police at roadblocks placed on the town perimeter.

In neighbouring Mongolia, a couple died of the bubonic plague in May after they ate raw marmot meat, another carrier of the plague germ.