Mexico's swine flu outbreak has the potential to turn into a worldwide pandemic, the head of the World Health Organisation (WHO) said on Saturday.

"It has pandemic potential because it is infecting people," WHO Director-General Margaret Chan said at a teleconference. But she also said it was too early to say whether the flu will turn into such a pandemic or not.

"However, we cannot say on the basis of currently available laboratory, epidemiological, and clinical evidence whether or not it will indeed cause a pandemic," she said.

Calling the swine flu a "serious situation," Chan warned that it must be monitored closely.

"We do not yet have a complete picture of the epidemiology or the risk, including possible spread beyond the currently affected areas," Chan said. "Nonetheless, in the assessment of WHO, this is a serious situation."

How the situation will evolve is "unpredictable," she said, urging other countries to "increase vigilance."

The Mexican government reported 20 deaths from the disease and it may be responsible for dozens of other deaths.

The new flu strain -- a mixture of swine, human and avian flu viruses has killed 68 people among 1,004 suspected cases in Mexico and infected eight in the United States. But the new virus is still poorly understood and the situation is evolving quickly, Chan warned.

(Xinhua News Agency April 26, 2009)