An explosive device was thrown during a protest outside the mayor’s official residence on Manhattan’s Upper East Side on Saturday, according to the NYPD.

Police say the incident happened near East 87th St. and East End Avenue, just outside Gracie Mansion.

Officials say two demonstrations were happening in the area at the time. One was a small rally called “Stop the Islamic Takeover of New York City,” organized by activists including far-right figure Jake Lang. A larger group of counter protesters gathered nearby for a demonstration called “Run the Nazis Out of New York City — Stand Against Hate.”

Police say tensions between the groups grew during the afternoon.

Investigators say an 18-year-old counter-protester lit a device and threw it toward the protest area. Authorities say the device appeared to be a jar wrapped in tape and filled with nuts, bolts and screws.

Video from the scene shows the device smoking as it traveled through the air before landing near police barricades and officers.

The city’s police commissioner, Jessica Tisch, later said the object was confirmed to be an improvised explosive device, or IED, that could have caused serious injury or death.

Police say the same person later received a second device from another man and lit it, but dropped it before it ignited.

Officers moved in and took both men into custody.

In total, police say six people were arrested during the events Saturday. That includes the two people accused of handling the devices, a protester accused of using pepper spray earlier in the demonstration, and others charged with disorderly conduct and obstructing traffic.

Later that day, investigators also found a suspicious device inside a parked car on East End Avenue between East 81st and East 82nd streets. Several streets were closed and some buildings were partially evacuated while the bomb squad examined the vehicle. Police later removed the car and reopened the streets.

In a statement posted on social media, Mayor Zohran Kwame Mamdani condemned the violence.

“Violence at a protest is never acceptable,” the mayor wrote. “The attempt to use an explosive device and hurt others is not only criminal, it is reprehensible and the antithesis of who we are.”

Police say they are working with federal prosecutors and the Federal Bureau of Investigation as the investigation continues. Officials say they are still testing the devices and trying to determine whether anyone else may have been involved.

Mayor Mamdani and Commissioner Tisch will provide an update on the investigation later Monday morning.