Three possible coronavirus cases are now under the radar of the World Health Organisation (WHO) but the global health agency has insisted that an outbreak is unlikely looming, reports said.

Citing reports by the UK Health Protection Agency (HPA), WHO spokesman Gregory Hartl told the Australian Associated Press (AAP) on Tuesday that three cases of SARS-like virus were now being investigated by health experts.

The first one, according to Mr Hartl, was recorded in Saudi Arabia, where a 60-year-old man died earlier this year of respiratory and kidney complications.

The second case, AAP said, involves a Qatari national currently in serious condition in a London hospital and is said to be infected with a virus similar to what was seen in the Saudi Arabia case.

The Wall Street Journal has reported on Monday that that Qatari patient had previously travelled to Saudi Arabia and "the virus that infected him bears a 99.5% similarity," to the Saudi victim.

The third case, Mr Hartl said, is still regarded by WHO experts as SARS suspect.

In a separate interview with ABC this morning, Mr Hartl said "we only have two confirmed cases and then in addition there's a suspect case. So all we know is that these two cases have occurred and they do not have any link."

WHO and other health experts remain clueless on how the new virus or viruses were transmitted, Mr Hartl said, adding that initial reports showed no evidence of human-to-human transmission.

"It's still very early days ... but all possible avenues of infection are being explored right now," the WHO representative told AAP.

Also, a U.S. expert has allayed fears that another SARS outbreak could erupt soon following the contagion in 2002 that killed close to 800 people mostly in China, The Associated Press (AP) reported yesterday.

"We don't know if this is going to turn into another SARS or if it will disappear into nothing," Michael Osterholm, a flu expert from the University of Minnesota, told AP on Monday.

Mr Osterholm warned though that common colds do not normally kill people, adding that the latest WHO report should give us "reason to think it might be more like SARS."

Bloomberg said that in previous cases of the disease, some 10 per cent of those afflicted eventually died.

Apart from the three cases reported both by the WHO and HPA, no new infections have yet to be reported by the British government, ABC said on Tuesday.

The Australian government, ABC added, is currently on alert but has advised the public that the present situation calls for no immediate concern.