Influenza patients between 10 and 17 who took Tamiflu were 54 per cent more likely to exhibit serious abnormal behaviour than those who did not take the antiflu drug, a final report from a Japanese Health, Labour and Welfare Ministry research team, said.

The team, led by Yoshio Hirota, a professor at Osaka City University, studied the cases of about 10,000 children under 18 who had been diagnosed with influenza since 2006.

It will soon submit the report to a safety research committee of the ministry's Pharmaceutical Affairs and Food Sanitation Council.

"The link with Tamiflu can't be ruled out," the report said. "New research should be carried out, focusing on serious abnormal behaviour."

The ministry suspended the use, in principle, of the drug by 10- to 19-year-olds in 2007 after a number of children behaved abnormally after taking it. Examples of such behaviour include one child who started to hop after taking the drug and another who tried to jump from a balcony. The new findings make it unlikely the ministry will lift the ban.