US pop icon Madonna hit out at Venezuelan President Nicolas Maduro on Tuesday, accusing his government of "fascism" over its handling of nationwide protests.

In a post alongside a picture of Maduro on image-sharing social network Instagram, Madonna accused the Venezuelan leader of human rights violations, while also condemning authorities in Russia and Ukraine.

"Apparantly (sic) Maduro is not familiar with the phrase "Human Rights"! Facism (sic) is alive and thriving in Venezuela and Russia," Madonna wrote. "The Ukraine isn't far behind!"

Venezuela has been gripped by weeks of protests that have left at least four people dead.

Demonstrators are angry over rampant street crime, runaway inflation, corruption and bleak job prospects in the country with the world's largest proven oil reserves.

Maduro, who took office after the death of Hugo Chavez last year, has claimed the protests are part of a conspiracy to overthrow his government.