New York City's top financial officer, who is running to be its next mayor, was handcuffed and arrested by federal agents while guiding a defendant out of immigration court on Tuesday.

Immigration and Customs Enforcement (ICE) agents detained Brad Lander, who is the city's comptroller, "for assaulting law enforcement and impeding a federal officer", a spokesperson said.

Lander, who was later released, said he "certainly did not" assault an officer.

The incident comes amid an immigration crackdown under President Donald Trump who has directed agents to conduct raids and deport immigrants who are in the US illegally.

Videos of the incident show Lander leading a man through the hallway and requesting that the agents show a judicial warrant to detain them.

A spokesperson for Lander's campaign said the comptroller was escorting a defendant out of immigration court when he was arrested.

"You don't have authority to arrest US citizens," Lander is heard telling ICE agents in the video as they put him in handcuffs.

But ICE said Lander was undermining officials.

"Our heroic ICE law enforcement officers face a 413% increase in assaults against them—it is wrong that politicians seeking higher office undermine law enforcement safety to get a viral moment," Homeland Security spokeswoman Tricia McLaughlin told the BBC. "No one is above the law, and if you lay a hand on a law enforcement officer, you will face consequences."

Upon his release, Lander said that no charges were being brought against him.

The comptroller said the man, who he identified as a man named Edgardo, "has been stripped of his due process rights by a government and a judge that owe him a credible threat hearing before they deport him".

"I will be fine, but Edgardo is not going to be fine, and the rule of law is not fine, and our constitutional democracy is not fine," Lander said referring to the man he was trying to escort out of immigration court.

New York Attorney General Letitia James called the arrest "profoundly unacceptable".

"Arresting Comptroller Lander for the simple act of standing up for immigrants and their civil rights is a shocking abuse of power," she said in a statement. "No one should face fear and intimidation in a courthouse, and this is a grotesque escalation of tensions. The administration's rampant targeting of New Yorkers only makes our communities less safe."

New York Civil Liberties Union Executive Director Donna Lieberman called on elected officials and candidates for office to condemn the arrest.

"ICE arresting Brad Lander for asking questions is a stunning abuse of power and a threat to our democracy," Ms Lieberman said. "Arresting a public official, the duly-elected comptroller of the City of New York, for asking questions is dangerous intimidation and shows a wanton disregard for the will of the people of New York.

It sends an unmistakably authoritarian message – that ICE doesn't care about the rule of law and that anyone exercising their right to challenge ICE and speak up for immigrants will be punished."

Trump's immigration crackdown has included cross-country raids and an increasing number of deportations, and also sparked days of protest against ICE, particularly in Los Angeles.