Cruz put the hosts ahead after 20 minutes when he ghosted behind Napoli defense to control Zlatan Ibrahimovic's neat pass inside the area and drill past keeper Gennaro Iezzo.

The Argentinean striker doubled the lead in the 36th minute after chesting down Dejan Stankovic's pinpoint long ball before firing a left-footed strike into the bottom corner.

He could have completed a hat-trick three minutes later when he was released by Luis Figo but his shot went just wide of the post.

Iezzo denied Inter a certain goal three minutes before the break when he superbly blocked Ibrahimovic's close-range volley.

Roberto Sosa gave the visitors a lifeline six minutes from time but the Nerazzurri held on to clinch all three points.

They lie on top of the standings with 17 points, four ahead of second-placed Juventus who take on Fiorentina on Sunday. Napoli are sixth on 10 points.