Cambodia has suffered its second outbreak of bird flu this year in the same province where the H5N1 virus killed a boy in April, officials said on Saturday.

The virus was confirmed in more than 1,300 ducks that died in Prey Veng province, 70 km (45 miles) southeast of Phnom Penh, but there were no immediate reports of human infections, they said.

"Yes, bird flu is back," senior Agriculture Ministry official Nou Muth said. "We have announced this outbreak to alert villagers not to handle dead poultry."

Most of the more than 130 people killed by the H5N1 virus, including six in Cambodia, have contracted the disease through close proximity to infected birds.

The virus has not yet shown the ability to mutate into a form that could pass easily between humans, causing a pandemic that might kill millions of people.

But experts fear it might, especially in a poor country like Cambodia, which is recovering from 30 years of civil war and where health surveillance systems are rudimentary at best.

"Bird flu is still the hot issue for us. We are still worrying that villagers in the affected are might have been selling their chickens or ducks to others secretly," Nou Muth said.

Several hundred domestic ducks, which can carry the H5N1 virus without necessarily showing symptoms, had been culled in within 3 km (2 miles) of the outbreak, agriculture official Yim Vanthan said.

Neighboring Thailand reported its first outbreak of the virus in eight months in July and reinvigorated a campaign to suppress it. Laos, which also has a long border with Cambodia, also reported an outbreak last month.