She had already closed some border operations, including cross-border ferries and high-speed rail services.
Only two border checkpoints – at Shenzhen Bay and the bridge to Macau and Zhuhai – will remain open, as well as the airport. But she added she could not rule out further measures should the situation change.
Doctors, nurses and medical personnel in Hong Kong had threatened a five-day strike this week in an attempt to force the city leaders to close down the multiple border crossings with the mainland.
The strike plans emerged as the city confirmed a 15th person had tested positive for coronavirus.
“We feel this is a war time,” one doctor told Sky News on condition of anonymity.
“We are not running away from our duty. We want to help our patients but we don’t feel like the Hong Kong government is doing enough to safeguard the people of Hong Kong.”
Ms Lam said the suspension of border crossings had “absolutely nothing” to do with the pressure from medical workers.
A growing list of countries around the world moved to isolate mainland China as the coronavirus claimed its first death outside the People’s Republic.
The victim had travelled from the epicentre of the outbreak in Wuhan, in the Chinese province of Hubei, before moving through three other provinces, going onto Hong Kong and then arriving in the Philippines where he reported ill.
The Philippines moved quickly to bar all those travelling from China, Hong Kong and Macau.
New Zealand joined a number of other countries including America, Australia, Singapore and Japan who have barred all those coming from China. They have so far stopped short of banning those from Hong Kong.
A 25,000 square metre, 1,000-bed hospital in Wuhan, which has been built in just eight days, opened its doors to its first coronavirus patients on Monday.
There appears to be no sign of the virus abating. Rather medics across the world are bracing themselves for a spike of cases in the coming weeks as visitors return from the extended Lunar New Year holidays.
None more so than those in Hong Kong where medics feel especially vulnerable because of their cross-boundary links with mainland China and the refusal by the authorities to completely seal off the territory.
Many of the territory’s pharmacies and shopping outlets have run out of surgical face masks and hand sanitisers. Those which have managed to secure batches of masks sell out within no time.
Hong Kong’s position as a major financial hub is likely to be doubly threatened: first, if the coronavirus takes a grip in the territory, and secondly, if the borders with the mainland are completely sealed off stifling a raft of international trade, movement and businesses.
