Libya's Islamist authorities say they are shocked to learn the U.N. envoy to their war-torn country has accepted a job from the United Arab Emirates, which backs their main political rival, the internationally recognized government.

The Islamist-backed government's statement Thursday demands an explanation from U.N. Secretary-General Ban Ki-moon.

The statement says Bernardino Leon's hiring to lead a state-backed think tank casts doubts on the U.N. envoy's credibility, especially at a critical time when Libya's rivals are being urged to accept his proposals as neutral.

The Guardian newspaper on Wednesday quoted an email from Leon to the UAE foreign minister saying he had a strategy to "completely delegitimize" the Islamist-backed government.

Leon told reporters Thursday that he sees no conflict of interest and that the proposed Libya peace agreement is unbiased.