The Venezuelan military is hunting for a rogue elite police officer suspected of carrying out a helicopter attack on the country's Supreme Court.
Oscar Pérez posted Instagram videos admitting the attack and calling on Venezuelans to rise up against the government of President Nicolás Maduro.
The officer's home has been searched as the president put the entire military on alert, citing a "terrorist attack".
The country is in the midst of a deep economic and political crisis.
Nobody was injured in the helicopter attack, which took place at around sunset on Tuesday evening.
One police source reported by Reuters said that the helicopter had been dumped in Higuerote, on the Caribbean coast, but that the pilot had not been found. The report has not been verified.
On Tuesday 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.
The helicopter, reportedly stolen, carried the marks of the CICPC forensic police force, for which Oscar Pérez has worked for 15 years.
Images on social media showed two occupants, one masked.
The government said 15 shots were fired at a social event at the interior ministry. The helicopter then flew to the court and dropped four Israeli-made grenades of "Colombian origin". One failed to detonate. No-one was injured.
Many of those opposed to Mr Maduro see the Supreme Court as one of his main supporters.
Mr 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."
Defence Minister Vladimir Padrino López urged Venezuelans to remain calm and stay vigilant.
State TV showed images of the pilot in front of the US Capitol building in Washington.
Mr Maduro has long claimed the US government is attempting to have him overthrown.
Opposition disputes authenticity of attack
Some of the president's opponents took to social media to suggest he was responsible for staging the helicopter attack in order to justify a further crackdown on dissent.
Julio Borges, leader of the opposition-controlled legislature, said: "It seems like a movie. Some people say it is a hoax, some say it is real, some say that it was police personnel who really are fed up.
"I summarise it like this: a government is decaying and rotting, while a nation is fighting for dignity."
Freddy Guevara, of the opposition MUD alliance, posted a tweet on Wednesday calling on people to continue to oppose the Maduro government.
He said: "Maduro knows that nobody supports him, so today more than ever we must continue in the street, generating pressure to overcome this dictatorship!"
Political unrest continues in Venezuela
There have been almost daily anti-government protests in Venezuela for more than two months as the country's economic and political crisis worsens.
Those opposed to the government say they are determined to keep protests going until fresh elections are called and the government is ousted.
More than 70 people have been killed in protest-related violence since 1 April, according to the chief prosecutor's office.