Four grenades were dropped on the court and 15 shots fired at the interior ministry on Tuesday, officials said.
Rogue policeman Oscar Pérez said he had piloted the stolen helicopter to attack what he called a "criminal government". His whereabouts are unknown.
What happened in the attack?
A blue police helicopter was seen flying over central Caracas carrying a banner reading "350 Freedom" - a reference to a clause in the constitution cited by opponents of Mr Maduro to claim his government is illegitimate.
How has the government responded?
President Maduro appeared on state television to denounce the attack.
He said: "I have activated the entire armed forces to defend the peace. And you can be assured that sooner or later, we are going to capture that helicopter and those that carried out this terror attack against the institutions of the country."
