A helicopter has dropped grenades on Venezuela’s Supreme Court in what President Nicolás Maduro called a “terrorist attack”.

Footage on social media shows a police helicopter circling over Caracas before shots and a loud bang are heard.

A police officer said to have piloted the stolen aircraft issued a statement denouncing the “criminal government”. His whereabouts are unknown.

The attack comes after mass protests against the political and economic crisis.

The Supreme Court is regularly criticized by the Venezuelan opposition for its rulings which bolster Nicolas Maduro’s hold on power.

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In an address from the presidential palace, Nicolas Maduro said the helicopter had flown over the Supreme Court and also the justice and interior ministries.

Officials quoted by Reuters said four grenades were dropped on the court and 15 shots had been fired at the interior ministry.

No injuries were reported but President Maduro said “a social event” had been taking place at the Supreme Court and the attack could have caused “dozens of deaths”. One of the grenades failed to detonate, he added.

Nicolas Maduro has placed the military on alert.

“I have activated the entire armed forces to defend the peace,” he said.

“Sooner or later, we are going to capture that helicopter and those who carried out this terror attack.”

The police officer identified himself as Oscar Pérez in video statements posted on the social media platform Instagram.

Appearing in military fatigues and flanked by armed, masked men in uniform, he appealed to Venezuelans to oppose “tyranny”.

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“We are a coalition of military employees, policemen and civilians who are looking for balance and are against this criminal government,” he said.

“We don’t belong to any political tendency or party. We are nationalists, patriots and institutionalists.”

Oscar Pérez said the “fight” was not against the security forces but “against the impunity of this government. It is against tyranny”.

It is not clear how much support, if any, the officer has.

Nicolas Maduro said the pilot had worked for former Interior and Justice Minister Miguel Rodriguez Torres, but was no longer with him.