Matt Damon will star opposite Leonardo DiCaprio in a new police thriller, Variety reports today.

The Martin Scorcese project - previously titled Internal Affairs - is set in Boston and follows a group of Irish-American mobsters in their ongoing battle with the police.

Damon has joined the cast of The Departed as a gangster who has infiltrated the Boston police department as part of its cadet class and has been steadily rising through the ranks.

DiCaprio will play a cop who's been deep undercover inside the mob and is starting to come unglued. Each side works feverishly to flush the mole out, with "deadly consequences."