AC Milan 4-0 Siena
Ronaldinho struck a first-half penalty, a second-half header and a long-range shot late on after Marco Borriello had hit the Rossoneri's second.
Siena's efforts to kick-start a dismal season were undermined by the 10th-minute dismissal of goalkeeper Gianluca Curci, which led to Ronaldinho's opening spot-kick as Leonardo's side cut Inter's lead after their 2-2 draw at Bari on Saturday.
AS Roma 3-0 Genoa
Luca Toni bagged his first goals since joining the Roma on loan from Bayern Munich this month, scoring on the stroke of half-time after team-mate Simone Perrotta had put Roma ahead in the 17th minute.
And Toni put the game beyond Genoa's reach on the hour mark to put the capital city club into 3rd spot.
Napoli 0-0 Palermo
Napoli drew 0-0 with Palermo in Naples in a dour game that had few real moments of danger after Fabrizio Miccoli missed a first half penalty for the visitors.
Chievo 1-0 Juventus
Juventus slipped to fifth in the standings after the Turin giants lost 1-0 at Chievo.
Gennaro Sardo's stunning first-half strike proved to be the only goal of the game as Juve turned in a performance lacking energy and confidence which comes on the back of a 3-0 hammering at the hands of AC Milan in their last league outing.
Serie A TOP SIX STANDINGS
CLUB Pl W D L GD Pts Inter Milan 20 14-4-2 +24 46 AC Milan 19 12-4-3 +16 40 AS Roma 20 10-5-5 +9 35 Napoli 20 9-7-4 +5 34 Juventus 20 10-3-7 +6 33 Palermo 20 8-7-5 +3 31