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BEIJING — The number of cases of a deadly new coronavirus climbed to close to 300 in China on Tuesday as health authorities in Asia and around the world stepped up screening at airports, at railway stations and on highways in an effort to stem the spread of the pneumonia-like disease.

On Monday, the head of a Chinese government expert team said human-to-human transmission of the virus had been confirmed.

The number of those killed by the virus rose to six, with cases being reported outside China — including in Thailand, Japan, Taiwan and South Korea. Health officials in Australia and the Philippines are also probing suspected cases of the virus.

Officials at China’s National Health Commission on Tuesday confirmed 291 cases of the disease — 270 of them in the country’s central Hubei province, home to the city of Wuhan, which has seen the majority of the cases. The number of detected cases in China stood at 62 on Sunday.

Five of those were reported in the capital Beijing, 14 in Guangdong, in southeast China, and two more in Shanghai, a global financial hub.

Thirteen more cases were reported by local health authorities across the country later Tuesday, bringing the number of confirmed cases to 304, although these cases are yet to be verified by the National Health Commission.

Travelers pass through a health screening checkpoint at Wuhan Tianhe International Airport in China on Tuesday, Jan. 21, 2020. Emily Wang / AP

Officials said they were also looking into 54 additional suspected cases in 14 provinces of the country.

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China's leading epidemiologist said Monday that over 95 percent of the cases were connected with Wuhan, either going in or out of the city.

Zhong Nanshan added that 14 members of medical personnel caring for coronavirus-infected patients have been infected.

The outbreak comes ahead of the Chinese Lunar New Year in late January, during which hundreds of millions of people are expected to travel domestically and overseas.

"More cases should be expected in other parts of China and possibly other countries in the coming days," said World Health Organization spokesman Tarik Jasarevic, according to Reuters.

At Wuhan Tianhe International Airport on Tuesday, thousands of passengers wore face masks as authorities stepped up screening measures amid holiday travel rush.

NBC News witnessed people exiting the airport being subjected to a body temperature screening test.

The Centers for Disease Control and Prevention said Monday that it was closely monitoring the outbreak, but the general risk for the American public was still deemed to be low.

The virus belongs to the large family of coronaviruses that can cause illnesses ranging from the common cold to more severe diseases such as the Severe Acute Respiratory Syndrome (SARS), which killed nearly 800 people globally during a 2002-03 outbreak that also started in China, paralyzing transport and damaging Asian economies.

The source of the outbreak is still under investigation in Wuhan, WHO said.

The agency will be holding an emergency committee meeting on Wednesday to discuss whether the virus constitutes a public health emergency of international concern, and formulate recommendations to manage the outbreak.

A medical staff member at Jinyintan hospital in Wuhan, China, where patients with pneumonia caused by the new strain of coronavirus are being treated. Darley Shen / Reuters

China's National Health Commission will also be holding a briefing on the coronavirus outbreak on Wednesday.

Over the weekend, three U.S. airports started screening passengers arriving from Wuhan to prevent the spread of the virus.

The South China Morning Post reported Tuesday that Beijing warned officials against covering up the spread of the virus, saying anyone who withheld information would face severe punishment and be “nailed on the pillar of shame for eternity.”

China had initially downplayed the full extent of the SARS outbreak in 2003.

But Chinese President Xi Jinping said Monday it was "extremely crucial" to take every possible measure to combat the virus.

Eric Baculinao and Dawn Liu reported from Beijing; Janis Frayer from Wuhan; and Yuliya Talmazan from London.