US air strikes on Venezuela and the seizing of the country's leader on the weekend clearly "undermined a fundamental principle of international law", the United Nations said on Tuesday.

"States must not threaten or use force against the territorial integrity or political independence of any state," Ravina Shamdasani, spokeswoman for the UN rights office, told reporters in Geneva.

"And this is what we are seeing," she said, calling on the international community to "come together with one voice... to make clear that this is an action that in contravention of the international law that was set up by member states".

US commandos backed by warplanes, the navy and air strikes, forcibly seized Venezuelan President Nicolas Maduro and his wife Cilia Flores in the early hours of Saturday.

Maduro appeared in court in New York on Monday to deny drug trafficking and other charges brought by Washington, insisting he had been kidnapped and remained Venezuela's president.

Shamdasani also dismissed US justifications for its actions, saying accountability for rights violations "cannot be achieved by unilateral military intervention in violation of international law".

"Using human rights arguments as a justification for this kind of military intervention is unacceptable," she said, adding that she feared the US intervention "will only make the situation worse". (AFP)