Oslo - Norway had as of Thursday registered a higher number of swine flu cases and fatalities than its Nordic neighbours, sparking speculation of a possible mutation of the A(H1N1) virus.

The Norwegian Institute of Public Health reported Norway has registered 13 deaths, neighbouring Sweden has to date had two, and Denmark none.

The institute however said that tests so far have shown that the virus was the same as in neighbouring countries.

The Norwegian Directorate of Health was to study the fatalities to determine if there were differences in how the patients were treated and set up a special register for seriously ill patients, Bjorn-Inge Larsen of the agency told broadcaster NRK.

Authorities have urged people to vaccinate themselves against the A(H1N1) virus, saying enough vaccines had been ordered for the whole population which amounts to 4.8 million.

Ongoing vaccinations of risk groups including people suffering from chronic heart or lung disease, or diabetes were to be concluded before the rest of the population would be offered vaccinations. (dpa)