A police helicopter dropped two grenades on Venezuela's Supreme Court building, President Nicolas Maduro said Tuesday in what he called a "terror attack".

Maduro said he has called up the military in response. 

"I have activated the entire armed forces to defend the peace," he said in a speech delivered from the Miraflores presidential palace.

"Sooner or later, we are going to capture that helicopter and those that carried out this terror attack," he declared.