Mexico City - The number of confirmed swine flu infections in Mexico climbed from 49 to 91, with eights deaths caused by the new strain, Mexican Health Minister Jose Angel Cordova said Wednesday night.

The latest figures came shortly after the World Health Organization (WHO) in Geneva raised the pandemic alert for swine flu by one level to phase 5.

The declaration of phase 5 by WHO Director General Margaret Chan is a strong signal that a pandemic is imminent, but not inevitable. The second-highest phase is characterized by human-to-human spread of the virus in at least two countries in one WHO region.

There have been close to 160 deaths and nearly 2,500 infections in Mexico's flu outbreak. Of these, more than 1,300 people remain in hospital, but most have not yet been identified as swine flu cases.

Apart from Mexico, which is the epicentre of the outbreak, WHO reported of confirmed swine flu cases in Canada, the United States, Israel, Spain, Britain and New Zealand. Costa Rica said it had two confirmed cases and 25 suspected cases were pending testing.

Chan said all countries should activate pandemic flu plans and called on governments and health authorities to be on high alert for influenza-like illnesses and pneumonia.

"The situation remains serious," Cordova said, adding that all non-essential state and federal government offices and private businesses would be closed until May 6. Only essential service providers such as hospitals, transport, supermarkets and garbage collectors were to remain open.

Mexico City's Finance Minister Mario Delgado told a press conference Wednesday that the government would give 50 pesos (about 4 dollars) per day to those workers who have suffered because of the limitations on movement and closure of several establishments.

Those hospitalized were to be compensated with 3,000 pesos (about 200 dollars), he said.

On Tuesday, Mexico City banned restaurants from serving food on their premises, although they can sell take-away meals. The move affected an estimated 35,000 restaurants and some 450,000 jobs.

Argentina suspended flights to and from Mexico from Wednesday until at least Monday, as it awaited test results of three suspected cases of swine flu.

Cuba Tuesday suspended flights to and from Mexico. The measure was to last 48 hours, but was later extended indefinitely, according to an official statement published Wednesday in Communist Party daily Granma.