As the H1N1 swine flu is reported to have claimed 152 lives in Mexico and is confirmed to have hit Europe, the whole world is on higher alert for the new deadly virus, with the World Health Organization raising its pandemic alert level.

About 2,000 people in Mexico have been hospitalized with swine flu as of Monday, 776 of them in serious condition, according to official statistics.

In a new preventive measure, the government ordered the cancellation of school activities at all levels, from kindergartens to universities, across the country through May 6.

Up to 40 cases of swine flu were confirmed in five states across the United States as of late Monday, prompting the government to release 25 percent of a federal drugs stockpile to states fighting the pandemic.

US health officials said the cases were in the New York city and the states of Ohio, Kansas, Texas and California.

A 51-year-old South Korean woman, among three back from a recent trip to Mexico, was confirmed the first suspected swine flu patient in the country early Tuesday.

The flu was designated by the South Korean government as an infectious livestock disease and allowed authorities to limit movement. The government also ordered to destroy and bury the sick animals, and compensate farmers if the outbreak of swine influenza is discovered in the country.

Scottish Health Minister Nicola Sturgeon confirmed Monday two people coming back from Mexico have been tested positive for swine flu in Britain.

The minister added that seven of the 22 who had been in contact with the two patients have developed "mild symptoms," but they have not been confirmed as swine flu cases and are being "appropriately cared for" at home.

In Spain, Health and Social Policy Minister Trinidad Jimenez also confirmed the first case of swine flu in the country.

Amid the rapid spread of swine flu in some countries, the World Health Organization (WHO) on Monday raised its pandemic alert level from Phase 3 to Phase 4, indicating a significantly increased risk of a pandemic, a global outbreak of a serious disease.

The increased alert under the advice and guidance of an emergency committee means the virus can cause sustained human-to-human transmission and "community-level outbreaks."

The tough situation impelled countries around the world to take precautious measures to protect themselves and stop the spread of the flu.

In Japan, a task force headed by Prime Minister Taro Aso has been set up to deal with the situation.

The Japanese government said it will conduct quarantine activities on flights from Canada and the United States at three of Japan's key international airports as well as on flights from Mexico, and will have quarantine officers check passengers in the cabin before they disembark the aircraft.

Romanian Deputy Prime Minister and Interior Minister Dan Nica said all measures suggested by the health ministry have been taken to prevent a possible outbreak of the flu in Romania.

At Germany's biggest air hub Frankfurt international airport, airline crews on jets coming from swine-flu-affected areas were instructed to report any sick passengers.

The Health Ministry of Cambodia planned to set up scanners at the Phnom Penh and the Siem Reap international airports to check travelers' body temperature against the possible entry of swine flu.

Cambodian health officials said all people who once traveled to the infected areas will be observed.

A string of countries including Norway, Sweden, Australia, Israel, France and Guatemala were testing suspected cases of the Mexican flu.

The Chinese Ministry of Health (MOH) has required local authorities to immediately organize experts to provide medical consultations and treatment at designated medical institutions if people were suspected to have contracted the virus, and has ordered medical institutions at all levels to step up monitoring of suspected swine flu cases, and to report them to the ministry promptly.

According to MOH spokesman Mao Qun, a diagnostic reagent for use in testing for swine flu is under development in China, and the research on a possible vaccine and medication to combat the deadly virus is also underway.

UN Secretary-General Ban-Ki moon told reporters the H1N1 swine flu is of "the most serious concern" to the international community, including the United Nations.

"We are concerned that this virus could cause a new influenza pandemic...It could be mild, in its effects, or potentially severe," he said.