China's state news agency says scientists have developed two vaccines to prevent the spread of the deadly H5N1 strain of bird flu.

Xinhua quoted the director of the China National Bird Flu Reference Laboratory, Chen Hualan as saying experiments show the new vaccines are 100 percent effective in preventing the spread of the virus.

Last week, China enacted emergency measures after confirming that the virus killed scores of migratory birds in the western Qinghai province. No human cases were reported.

The World Health Organization recently said a study suggests the virus is mutating in ways that could pose a greater threat to humans. Experts have warned that such a mutation could kill millions.

The virus has killed more than 50 people in Vietnam, Thailand and Cambodia.

Some information for this report provided by AP and Reuters.