US federal prosecutors have arraigned two men detained by New York City Police on Saturday under suspicion of terrorism in an incident involving improvised explosive devices (IEDs) thrown at far-right agitators during an anti-Islam protest outside the mayor's residence, Gracie Mansion.

Current Mayor Zohran Mamdani is the first Muslim elected to the office. He was not home when the incident occurred.

The Saturday IED attack took place during a stand-off between a group of about 20 people decrying what they said was the "Islamification of New York and America" and a group of roughly 125 anti-fascist counterprotesters.

Why were Christian nationalists protesting in front of NY Mayor Mamdani's home?

The anti-Muslim protest was organized by far-right agitator Jake Lang, a white Christian nationalist who was jailed for his participation in the January 6 insurrection at the US Capitol and has a long criminal record of assaults, civil disorder and other crimes.

A scuffle reportedly broke out shortly after the protest began, with police arresting one member of Lang's group for pepper-spraying counterprotesters.

Shortly thereafter, one of the explosive devices was reportedly thrown at the anti-Islam group and soon after that another IED was planted near police.

Over the weekend, Mamdani released a statement condemning Lang's protest as being "rooted in bigotry and racism," emphasizing: "Such hate has no place in New York City. It is an affront to our city's values and the unity that defines who we are."

"What followed," added Mamdani, "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, it is reprehensible and the antithesis of who we are."

Pennsylvania IED-makers suspected of having Islamist motives

Two male suspects are under investigation for possible terror motives in the incident. 

On Monday morning, Police Commissioner Jessica Tisch told reporters that the incident "is being investigated as an act of ISIS [Islamic State] inspired terrorism." 

Mamdani, standing alongside Tisch in front of Gracie Mansion, told reporters that the 18 and 19-year-old suspects had, "traveled from Pennsylvania and attempted to bring violence to New York City."

Jake Lang attempted to disrupt the mayor's comments from beyond Gracie Mansion's gates.

Saturday's incident involved the throwing of two glass preserve jars filled with screws and bolts, wrapped in duct tape, and outfitted with fuses and explosive charges. Though the fuses were lit, neither device exploded. Tisch said they were functional.

On Sunday, Tisch said the NYPD bomb squad had determined that the first device it examined was "not a hoax device or a smoke bomb. It is, in fact, an improvised explosive device that could have caused serious injury or death."

"Further analysis will be conducted, including on a second device," she added.

An AFP correspondent at the scene said one of the suspects shouted Allahu Akbar, or "god is most great" when he threw the first device.

Authorities have conducted searches at two Pennsylvania homes since taking the men into custody as well as inspecting a car near the scene of Saturday's incident. 

Commissioner Tisch said that although an Islamist terror angle is being investigated, the incident did not appear to be connected to the current US-Israeli war with Iran.

She did not elaborate on why authorities suspect an ISIS link.

AG Bondi: US wont allow 'anti-American ideology to threaten this nation'

The two men were arraigned Monday on charges that include attempting to provide material support to a foreign terrorist organization and using a weapon of mass destruction.

The defendants said nothing in court, but reportedly smirked as the judge read out allegations of their support of the Islamic State group. 

The complaint filed against them claimed that one had yelled that "ISIS" made him carry out his attempted attack. Both men confessed that they had sworn allegiance to the Islamist terror outfit.

When asked if they had hoped to emulate the 2013 Boston Marathon bombing that killed three and injured hundreds, one of the suspects reportedly told authorities that he had hoped to cause much more bloodshed.

Police Commissioner Jessica Tisch said neither defendant has a criminal history.

US Attorney General Pam Bondi took to social media on Monday vowing that law enforcement "will not allow ISIS's poisonous, anti-American ideology to threaten this nation."

Police and federal prosecutors will hold a press conference later on Monday.

Edited by: Jenipher Camino Gonzalez