* Milan extend lead to five points with home victory
* Controversial penalty rocks Napoli who barely threaten (adds details)
A hotly-contested penalty set Serie A leaders AC Milan on their way to a 3-0 home win over title rivals Napoli on Monday which extended their advantage at the top to five points.
Zlatan Ibrahimovic blasted in the spot-kick early in the second half after Salvatore Aronica was adjudged either to have handled or used an arm to block Alexandre Pato, with replays inconclusive.
Napoli players went crazy at the decision, jostling the referee, but Milan felt justice was done after having two earlier penalty shouts on Ibrahimovic and Mark van Bommel turned down in a largely low quality game played in heavy rain.
Substitute Kevin Prince Boateng made it 2-0 from Pato's pass on 77 minutes and Brazil striker Pato curled in an excellent third soon after as a toothless Napoli barely had a shot.
Third-placed Napoli's defeat meant champions Inter Milan, led by last season's Milan coach Leonardo, stayed in second spot after Sunday's 2-0 win at Sampdoria.
Milan travel to traditional rivals Juventus next weekend and face Inter in the city derby on April 3 but with just 11 games left their chances of a first scudetto since 2004 look good after swatting aside one their big threats.
The heart both sides showed was an advert for the Italian game but the constant misplaced passes were not in a month where Serie A teams have struggled in European competition.
Ibrahimovic and Gennaro Gattuso lashed over for Milan in the opening stages and defensive midfielder Van Bommel was the unlikely man on the end of their two best chances before the break.
Marek Hamsik shot wide from distance in a rare Napoli foray forward as top scorer Edinson Cavani struggled to get into the game and Walter Mazzarri's side, last champions in 1990 with Diego Maradona, badly missed suspended forward Ezequiel Lavezzi.
Milan finally broke through four minutes into the second period but their players, the San Siro crowd and coach Massimiliano Allegri were as surprised as anyone when referee Gianluca Rocchi pointed to the spot.
Napoli's surprise title challenge, from a club who went out of business in 2004 and re-formed in the lower leagues, now looks in jeopardy with a six-point gap to make up.