Security is being beefed up at arenas and stadiums across the city to combat potential terror threats.

That means new weapons too.

Police say officers are being trained in the use of the M4 rifle — a shorter, lighter version of the M16 assault rifle.

The precinct level officers will wear tactical uniform items, including heavy vests and helmets.

They're being assigned to venues like Madison Square Garden and Barclays Center.

Coverage at outdoor venues like Yankee Stadium and Citi Field will begin next year.