Jakarta - Indonesia, the country worst hit by bird flu, on Thursday warned its citizens against travelling to Mexico and eight other countries that have been hit by an outbreak of swine flu.

Authorities were also tightening control at all entry points to prevent the spread of swine flu to the country, said Bayu Krisnamurthi, head of Indonesia's commission dealing with bird flu.

He announced the move after the World Health Organization Wednesday night upgraded its influenza alert level to phase 5, which means the world is facing an imminent risk of a pandemic from swine flu. Phase 6 is the highest state of alert.

"Indonesia is ready to implement its pandemic preparedness and response plan," Bayu said in a news conference.

"We are stepping up surveillance and early detection efforts as well as control at airports, seaports and land borders," he said.

Bayu said the advisory did not amount to a travel ban

Indonesia, which has imposed a ban on pork imports, has a stockpile of 3 million doses of Tamiflu antivirals and countries with excess supplies had expressed readiness to help if needed, Bayu said.

Indonesia has the highest death toll in the world from the H5N1 bird flu virus, with 119 fatalities.

Mexico has confirmed 91 infections from the H1N1 swine flu virus and eight deaths although 159 people have died there recently of the flu. The United States has reported one death from swine flu.

Other countries reporting infections but no deaths are Canada, Britain, Spain, New Zealand, Germany, Israel and Austria.