Adults and children who are severely ill with H1N1 flu or at high risk of complications should be treated with antivirals like Tamiflu, the World Health Organization (WHO) said on Wednesday.

But otherwise healthy people with mild flu-like symptoms need not be given the drugs to combat swine flu, it said.

The United Nations agency reiterated advice first issued on May 21 on the use of antivirals for patients infected with the H1N1 virus, which applies to patients above one year old.

"WHO continues to recommend use of antivirals as treatment for people who are severely ill or are at risk of other health complications," it said in a statement sent to journalists.

Prompt antiviral treatment with oseltamivir, the generic name for Tamiflu made by Swiss drug maker Roche Holding, is recommended for "at risk" groups including pregnant women.

"Antivirals need not be administered for otherwise healthy individuals with mild flu like symptoms," it said.

British researchers said this week that children should not routinely be treated with flu drugs like Tamiflu since there is no clear evidence they prevent complications and the medicines may do more harm than good.

They called for a rethink of current widespread use of antivirals among under-12s in the light of an analysis of clinical data from past outbreaks of seasonal flu showing scant benefits and potentially harmful side effects.

In its statement, the WHO said its expert panel had recently reviewed its guidance on the use of antivirals as treatment for patients with H1N1 pandemic flu.

The experts had considered clinical evidence, including that used in the British Medical Journal for review, which the WHO noted had concerned seasonal and not pandemic H1N1 flu.

"The recommendation doesn't change," WHO spokeswoman Alphaluck Bhatiasevi told Reuters.

Roche said there were significant clinical data showing Tamiflu to be effective and well tolerated in children, and the data had been taken into account by both U.S. and European drug regulators in approving the medicine for youngsters.