The helicopter was apparently stolen and piloted by an officer in the country's investigative police force, Oscar Perez. As it strafed the court building and the Interior Ministry in Caracas, the attackers fired gunshots and lobbed grenades, officials said.

Maduro condemned the attack as an attempted coup, saying "terrorists" were behind the offensive and that an operation was underway to track the perpetrators down.

But much remained murky about the assault: if it was an attempt to unseat Maduro's government, it was a spectacular failure. No one was injured and one of the grenades failed to explode, government officials said. 

It was unclear how a rogue police helicopter could have circled high-profile buildings in the Venezuelan capital without being shot down. Eyewitnesses and local journalists said the assault went on for about two hours.