Manila- The Philippines released three people from quarantine after they tested negative for swine flu despite exhibiting symptoms of the virus, the country's health chief said Thursday.

Four more people from Ireland, Britain, the United States and Canada remain hospitalized, pending the results of their laboratory tests, Health Secretary Francisco Duque said.

The released patients were two South Koreans and a male Filipino patient, according to the National Center for Disease and Prevention Control.

"The three have been sent home last night (Wednesday)," Duque said in a television interview.

Three of those who remained under quarantine are Filipinos who came from Ireland, the United States and Canada while one is a British national.

Duque urged the public to remain vigilant and told it not to panic because there has so far been no confirmed case of swine flu in the country.

He said the government has intensified monitoring and surveillance in airports and seaports to prevent the disease from entering the country.

According to the World Health Organization, 23 countries have reported 1,893 cases of the H1N1 strain of the flu virus. Mexico has confirmed 942 cases, including 29 deaths, while the United States has reported 642 cases and two deaths. (dpa)