An improvised explosive device thrown during protests outside New York Mayor Zohran Mamdani's home could have been deadly, police said. 

A jar filled with nuts, ‌bolts and screws, that was wrapped in black tape with a fuse, landed in front of police during a counter-protester at the "Stop the Islamic Takeover of New York City" demonstration.

But the fuse on the smoking IED extinguished itself without any explosion, according to New York ​City Police Commissioner Jessica Tisch.

The device was one of two that were thrown during the clashes, which broke out between two rival groups on Saturday, police said.

An NYPD bomb squad determined the object wasn't a hoax or smoke bomb, but an "improvised explosive device that could have caused serious injury or death".

After the first homemade weapon was thrown, the same suspect was then handed a second device from another demonstrator, which was dropped and did not appear to ignite, the commissioner added.

Two teenagers were arrested at the scene and taken into custody, while the second device is being examined, Commissioner Tisch ​said.

Another four were arrested in connection with the disturbances, including a suspect who deployed pepper spray and three others for disorderly conduct and obstructing traffic.

Later the next day, investigators found another suspicious package in a car a few streets from the mayor's Gracie Mansion in Manhattan's East End Avenue.

Several streets were closed and "limited evacuations of buildings" were ordered as the bomb squad assessed and removed the device, police said.

At around 7pm on Sunday, police used a flatbed truck to remove a Honda Civic and the streets were reopened.

New York police are working with the ⁠FBI and ​the US Department of Justice on the investigation.

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The protest, led by far-right activist Jake Lang outside Gracie Mansion, where Mr Mamdani lives with his wife in Manhattan, was met by a far larger group of counter-protesters.

Commissioner Tisch said she did not believe Mr Mamdani and his wife were home ​at the time of the violence.

In a statement on Sunday, Mr Mamdani condemned Mr Lang's protest but said the violence ​that followed it was more disturbing.

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

A person linked with Mr Lang's protest was one of the arrested suspects and charged with reckless endangerment, assault and unlawful possession of a noxious matter after allegedly macing counter-demonstrators, police said.

Mr Lang was previously charged with assaulting an officer with a baseball bat, civil disorder and other crimes before being pardoned as part of President Donald Trump's sweeping act of clemency for defendants connected to the January 6 riots in Washington DC.