US President Donald Trump has fired the independent inspector general for the US Agency for International Development (USAID), US media outlets reported on Wednesday.

Paul Martin's dismissal came a day after his office issued a report critical of the Trump administration's efforts to dismantle the agency, the Washington Post, CNN and others reported.

They cited a two-sentence email from the White House sent on Tuesday to Martin telling him his position was "terminated, effective immediately," but with no explanation of the reasons for the decision.

His office's report had warned that more than $489 million in food assistance was at risk of spoilage or potential diversion after the Trump administration implemented an aid freeze and stop-work order.