A two-year-old boy has died of bird flu in Indonesia, the health ministry said, bringing the country's death toll from the virulent disease this year to seven.

The toddler, from the city of Pekanbaru on Sumatra island, developed fever on April 17 and was hospitalised three days later, according to a health ministry statement released late Tuesday.

"His condition worsened and he died on April 27," it said.

It added that it was suspected that he contracted the virus through contact with poultry products as his parents sold quails' eggs for a living.

Indonesia is the nation hardest-hit by bird flu, with 156 deaths reported since 2003, according to the latest figures given by the World Health Organization, which exclude the country's latest death.

The virus typically spreads from birds to humans through direct contact, but experts fear it could mutate into a form that is easily transmissible between humans.