The H1N1 flu, also known as the swine flu, is proving more virulent than had previously been thought, French Health Minister Roselyne Bachelot was quoted as saying Monday.

"Summer is usually less favourable for the contamination by the virus but, contrary to what we had hoped, we are not registering a summer pause" in the spread of the disease, Bachelot told the daily Le Parisien.

Bachelot said it was possible that summer actually aided the spread of the virus because people traveled more and were more sociable.

She said that France would triple the number of hospitals, to more than 300, equipped to take charge of H1N1 flu cases.

France currently counted 276 confirmed cases of the illness, and another 258 people showing symptoms of the disease were being investigated.

At the weekend, eight schools were shut in France after pupils fell ill because of the H1N1 flu.