A virus that has killed 25 children and infected thousands across China will not threaten Beijing's Olympic Games in August, the World Health Organisation (WHO) said in comments published on Monday.

Health authorities in China have been battling to contain outbreaks of EV71, a sometimes fatal intestinal virus that has broken out in separate areas of eastern and southern China.

In Fuyang, a city in China's eastern Anhui province, 22 children have died and at least 5,151 people have been infected province-wide. Three people have died in southern Guangdong province.

"I don't see it at all as a threat to the Olympics or any upcoming events," state media quoted WHO China representative Hans Troedsson as saying.

"I think we need to do more research to understand the disease better and the WHO is providing technical advice and support to China."

EV71 can cause hand, foot, and mouth disease, which is characterised by fever, sores in the mouth and a rash with blisters - a common illness among infants and children but which is usually not fatal, according to the U.S. National Center for Infectious Diseases.

There is no vaccine or antiviral agent available to treat or prevent EV71. Enteroviruses spread mostly through contact with infected blisters or faeces and can cause high fever, paralysis and swelling of the brain.

The disease began spreading in Anhui in early March. But a delay in reporting it to the public until last weekend triggered criticism in the media, which said local government officials should be sacked.

Health officials say there was no cover-up in Anhui and the reason for the delay was that medical teams were trying to work out what the illness was.

China has issued a nationwide alert in a bid to control the disease, closing kindergartens and sending officials to visit nurseries and primary schools and educate staff on hygiene and prevention.

Twelve children remain in critical condition, and more than 600 in hospital in Fuyang alone, some with damaged brains, hearts and lungs, the China Daily said.

The Ministry of Health has warned that cases of hand, foot and mouth disease could increase with June and July being the peak months for the disease.

Hand, foot and mouth disease has been reported this year, without fatalities in several other eastern and central Chinese provinces, according to state media.