GENEVA — The World Health Organization said Tuesday that two members of an expert panel reviewing the global body's response to the swine flu outbreak have resigned over concerns about perceived conflict of interest.

John MacKenzie and Tony Evans stepped down because their close association with the UN health organization during the outbreak could be seen as conflicting with the panel's ability to remain independent, WHO said.

"Both have been closely engaged in deliberations at WHO which our committee is charged to review," said panel chairman Harvey Fineberg. "They each concluded it would be better to avoid the position as reviewer of their own earlier actions."

Mackenzie, a professor of tropical infectious diseases at Curtin University in Australia, and Evans, medical chief of the Montreal-based International Civil Aviation Organization, were on the emergency committee that advised WHO's Director-General Margaret Chan before she declared swine flu a pandemic.

WHO convened the panel in April to conduct a "credible and independent review" of how it and national authorities handled the outbreak. Concerns were raised at the time that several panel members were trusted WHO advisers and government employees who could end up whitewashing any failures.

The review panel will present a final report next year.