New York officials and the FBI have launched an investigation into "an act of ISIS-inspired terrorism", following the attempted use of two homemade explosives near the official residence of New York City Mayor Zohran Mamdani on Saturday.

The devices - which were both ignited, and at least one of which was thrown - "could have caused serious injury or death", New York City Police Commissioner Jessica Tisch said.

The incident occurred after a group of anti-Islam protesters gathered outside Mamdani's mayoral residence, Gracie Mansion, and clashed with a larger group of counter-protesters.

Two men who appeared agitated by the anti-Islam protesters have been arrested in connection with the devices.

he suspects were identified as 18-year-old Emir Balat and 19-year-old Ibrahim Kayumi, both from Pennsylvania.

"We were fortunate that the devices used this weekend did not cause the kind of harm that they were certainly capable of causing," Tisch said during a news conference on Monday. "But luck is never a strategy. Devices like these have the potential to cause devastating harm."

Tisch said the New York City Police Department (NYPD) remained vigilant in its counter-terrorism investigations and thanked two of the officers who stepped forward "without hesitation and without regard for their own safety", after the devices were lit.

Tisch said an analysis of one of the devices showed it was made of triacetone triperoxide - "a dangerous and highly volatile homemade explosive".

Tisch also said that officers had found a car in the city's Upper East Side that was tied to the two suspects. The NYPD used a robot that found "another possible suspicious device and materials inside the car consistent with the first two explosive devices".

In an earlier update, over the weekend, Tisch told reporters the protest was organised by Jake Lang, a far-right influencer and pardoned 6 January rioter. That group was outnumbered by the counter-protest, which had over 100 participants.

As the two groups clashed, video from the scene confirmed by the BBC's media partner, CBS News, showed Balat throwing the first "ignited device", which extinguished itself after striking a barrier.

Balat then retrieved a second device from Kayumi, lit it, and started running before later dropping it, Tisch said. In the updates provided on Monday, Mamdani said both devices had been thrown.

A preliminary analysis of one of the devices determined that it was "an improvised explosive device that could have caused serious injury or death", Tisch also wrote on X.

The devices were reportedly made from glass bottles filled with explosive material and surrounded by fragmentation, or nuts and bolts, with a firework-type fuse.

"The FBI and NYPD confirmed the suspicious items to be improvised explosive devices (IEDs)", the FBI wrote on X.

"Additionally, the FBI Joint Terrorism Task Force (JTTF) will be conducting interviews, reviewing videos, collecting evidence, and chasing down all leads."

Police also arrested Ian McGuiness, 21, for allegedly using pepper spray on counter-protesters. He and three others were charged with disorderly conduct and obstruction.

In a statement on Sunday, Mamdani called the anti-Islam protest "rooted in bigotry and racism" but said what followed was "even more disturbing".

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