Armed suspect attempts to breach FBI's Cincinnati office in US state of Ohio

An armed suspect attempted "to breach" the FBI Cincinnati Field Office in the US state of Ohio, the bureau said Thursday.

The individual attempted to get into the office's Visitor Screening Facility when an alarm was activated and agents responded, the bureau said in a statement. The suspect then fled northbound on Interstate 71.

"The FBI, Ohio State Highway Patrol, and local law enforcement partners are on scene near Wilmington, Ohio, trying to resolve this critical incident," it said.

The man was armed with an AR-15-style assault rifle, and fired a nail gun into the building before fleeing in a car, NBC News reported, citing anonymous law enforcement sources.

The Clinton County Emergency Management Agency said officers exchanged fire with an armed male suspect who is wearing a gray shirt and body armor. The standoff is ongoing and a lockdown has been imposed near Interstate 71, and the highway had been closed in both directions

People in the surrounding area should remain inside and keep their doors locked, said the agency.

The standoff comes as the FBI faces mounting pressure from Republicans after the bureau raided former President Donald Trump's Mar-a-Lago estate in the state of Florida.

The bureau has not yet explained the operation but Republicans have sought to frame the incident as a weaponization of the bureau to attack political rivals.