The World Health Organisation said Tuesday that it was valid to assume that most of the cases of influenza reportedly sweeping through Ukraine were caused by the pandemic A(H1N1) virus.

Ukrainian authorities on Sunday launched an urgent appeal for help from world powers after it imposed drastic measures to tackle a sudden surge of flu-like illness in the country.

More than 250,000 cases have been reported, according to official Ukrainian figures cited by the WHO.

- Given the potential significance of this outbreak as an early warning signal, WHO commends the government of Ukraine for its transparent reporting and open sharing of samples - the UN health agency said in a statement.

- Laboratory testing in Ukraine has confirmed pandemic H1N1 influenza virus in samples taken from patients in two of the most affected regions - it added.

- As the pandemic virus has rapidly become the dominant influenza strain worldwide, it can be assumed that most cases of influenza in Ukraine are caused by the H1N1 virus. -

The highest rates of "acute respiratory illness/influenza-like illness" were found in western areas, while they were also increasing rapidly around the capital Kiev, according to the WHO.

Seventy-one people have died as a result of flu and acute respiratory infections, the Ukrainian health ministry said, but the pandemic A(H1N1) virus has been confirmed in only one of the fatal cases.

The WHO said a team of specialists who arrived in the country on Monday will initially focus on the Lviv region, where reported "severe" cases of acute respiratory illness "have been especially high."

Samples from Ukraine have also been received by the WHO's influenza research laboratory in London for tests.

- Many questions remain to be answered - the WHO said.

- The outbreak in Ukraine may be indicative of how the virus can behave in the northern hemisphere during the winter season, particularly in health care settings typically found in eastern Europe - it added.

Local analysts have suggested that rival Ukrainian leaders may be trying to exploit popular fears in campaigning ahead of January 17 presidential polls, as each candidate seeks to take the initiative in fighting the outbreak.