The helicopter assault comes a day after Maduro announced the arrests of five opponents he accused of plotting against him.
The helicopter assault comes a day after Maduro announced the arrests of five opponents he accused of plotting against him to clear the way for a US invasion.
The beleaguered president, who for weeks has been thundering about alleged coup attempts against him, said the helicopter was flown by a pilot who worked for a former minister.
Around 15 shots were fired at the Interior Ministry, Maduro added.
"I have activated the entire armed forces to defend the peace," he said in remarks from the Miraflores presidential palace.
"Sooner or later, we are going to capture that helicopter and those that carried out this terror attack.”
No one was hurt in the incident, he said.
The government identified the helicopter pilot as a former member of Venezuela's main police force, known as the CICPC.
Maduro called on the opposition MUD alliance to denounce the attack but one of its leaders, Freddy Guevara, tweeted there was not yet enough information to comment.
Guevara urged people to take part in anti-government rallies Wednesday -- the latest in nearly three months of daily streets protests that have left 76 people dead.
Photos circulating on social media showed a helicopter flying over Caracas with a banner that read "350 Freedom" -- alluding to a constitutional clause recently invoked by the opposition to assert the Maduro government's lack of legitimacy.
The photos showed two people on the chopper, one with his face covered with a mask and the other with it visible.
Videos on social media showed a man who identified himself as a CICPC detective and said he was fighting tyranny, wants Maduro to resign and for Venezuela to hold early elections.
Earlier Tuesday, Maduro repeated claims of a US-backed coup attempt and angrily warned President Donald Trump that Venezuela would fight back against such a move.
"If Venezuela were dragged into chaos and violence... we would fight," Maduro bellowed in a speech to supporters.
If a coup prevented his side fulfilling his contested reform plans, he said, "we would achieve it by arms."
He said an armed intervention in his country would spark a crisis that would dwarf those caused by conflicts in the Middle East.
Addressing Trump, he said: "You are responsible for restraining the madness of the Venezuelan right-wing."
The opposition regularly accuses Maduro of repressing and jailing opponents. Judicial NGO Foro Penal says there are 383 political prisoners in Venezuela.
Addressing a crowd over the weekend, Maduro said detainees would face military trial over an alleged coup plot, backed by Venezuelan opposition leaders and aimed at precipitating a US intervention in the country.
"I am not exaggerating when I say it would have involved the arrival of American ships and troops in Venezuelan waters, on Venezuelan soil," Maduro said.
And on Saturday the head of the Organization of American States dug his heels in a war of words with Caracas, flatly rejecting its demand that he resign.
Maduro had suggested that Luis Almagro -- who has criticized the Venezuelan government for violating human rights, interfering in elections and detaining political prisoners -- step down in exchange for the country's continued membership in the regional body.
Though Almagro dismissed that notion, the OAS General Assembly was unable to reach agreement on a plan to deal with the instability in Venezuela at a meeting in Cancun last week.