An operation is underway at Sydney Airport after a firearm was discharged as federal police officers attempted to arrest a man inside a domestic terminal.

A crime scene has been sectioned off in the T2 terminal. 

The ABC understands the man was being detained by officers in a struggle when the police gun was fired. 

The Australian Federal Police (AFP) confirmed the man had been arrested.

Crime scene tape at Sydney Airport

The man was arrested inside the T2 terminal on Wednesday morning. (Supplied)

“An investigation into the incident has been launched … and there is no ongoing threat to the public,” a spokesperson said. 

“Further comment will be provided at an appropriate time.”

In a statement, Sydney Airport said it was assisting the AFP following the incident.

“No injuries occurred as a result of the incident. An arrest has been made and the airport is operating normally,” it said.