World health officials stepped up the battle against swine flu after Mexico upped the probable death toll from the epidemic to 103 and the United States declared a public emergency.

Mexican Health Minister Jose Angel Cordova said the number of both suspected and confirmed fatalities from swine flu has reached 103, and the number of those hospitalized due to the epidemic stood at about 400.

The previous probable death toll, announced Saturday, was 81 confirmed and suspected swine flu deaths.

The number of cases under observation in Mexico has reached 1,614, up from 1,324, Cordova said on national television.

Panic grew across the Latin American nation as citizens heeded government warnings to avoid contact with each other.

The United States will screen visitors arriving from infected areas, Homeland Security Secretary Janet Napolitano said Sunday, as 20 cases were confirmed in five states.

Suspected cases were also investigated in Europe, the Middle East and Asia , and six new infections were confirmed in Canada.

The European Commission called Monday for an urgent meeting of EU health ministers to discuss the possible threat posed by the swine flu outbreak, a spokesman said.

EU Health Commissioner Androulla Vassiliou will ask the EU's Czech presidency to organise the meeting, the spokesman said.

The commissioner wanted the talks to take place "as soon as possible", her spokeswoman said. Vassiliou was due to travel to Luxembourg Monday to hold talks on the outbreak with EU foreign ministers.

Confirmed cases in the US

Swedish Foreign Minister Carl Bildt, whose country will assume the EU presidency in July, called for calm, saying there was no need for panic in Europe.

"I don't think we should have undue worries until we know what's happening," he told reporters.

As thousands of panicked Mexicans wore surgical masks on the streets, President Felipe Calderon called for calm, urging citizens to work with authorities to contain the virus.

Mexico City was deserted Sunday after its 20 million residents were ordered to avoid crowds, and a soccer game at 105,000-seat Aztec stadium was played with no fans.

People stocked up on food and bottled water, preparing to spend days at home.

"As we look for cases of swine flu, we are seeing more cases of swine flu. We expect to see more cases of swine flu," Richard Besser, the acting head of the Centers for Disease Control, told a White House press conference.

Besser said there were eight confirmed cases in New York City, seven in California, two in Texas, two in Kansas and one in Ohio.

US President Barack Obama is monitoring the swine flu outbreak closely and has ordered a "very active, aggressive, and coordinated response," said White House homeland security advisor John Brennan.

Homeland Security Secretary Janet Napolitano said the US government was declaring a public health emergency - "standard operating procedure," she said - to expedite the testing and treatment of flu cases, particularly among young children, and to free up funds for anti-virals.

The World Health Organization warned the new strain, apparently born when human and avian flu viruses infected pigs and became mixed, could further mutate.

"Yes, it's quite possible for this virus to evolve," Keiji Fukuda, acting WHO assistant director-general for health, security and the environment, told journalists in Geneva.

First case in the Middle East

The WHO has already recommended that all nations "intensify surveillance for unusual outbreaks of influenza-like illness and severe pneumonia."

In the first suspected case in the Middle East, a 26-year-old Israeli was hospitalized in Netanya on returning from Mexico, hospital officials told AFP.

China meanwhile Monday joined Russia in banning pork imports from Mexico and some US states, although US officials said it was virtually impossible to catch the flu from eating meat.

"Eating properly handled and cooked pork or pork products is safe," US Agriculture Secretary Tom Vilsack said in a statement.

-AFP