Roma made the most of Juventus' slip-up on Saturday with a 3-1 win at Verona, while Milan scored two late goals to beat Cagliari 2-1.
After 10-man Juve were held to a 1-1 draw at Lazio, Roma closed to within six points of the champions with an impressive away win.
Adem Ljajic opened the scoring on the stroke of half-time but Verona, who entered the game on the back of successive defeats, levelled in the 49th minute through Emil Hallfredsson.
Gervinho, who scored the winner against Juventus in Roma's 1-0 Coppa Italia quarter-final win on Tuesday, restored the lead for Rudi Garcia's side on the hour-mark.
And a late Francesco Totti penalty sealed all three points for the capital club, who have won five matches in a row in all competitions.
Giampaolo Pazzini and Mario Balotelli scored in the last three minutes as Milan clinched a 2-1 come-from-behind win at Cagliari.
The hosts looked on course for their first victory against Milan since 1998 after Marco Sau's clever finish in the 28th minute.
Milan missed a host of chances to equalise but with three minutes left, Balotelli again stepped up for new head coach Clarence Seedorf, curling in an excellent free-kick.
And Pazzini, introduced as a substitute for Robinho on the hour-mark, hooked in Keisuke Honda's corner in the 89th minute, as his first league goal of the season gave Milan back-to-back Serie A wins for the first time this season.
Fiorentina missed the chance to close within one point of the fourth-placed Napoli after being held to a 3-3 draw against Genoa.
Genoa took the lead twice in the first half, through Alberto Gilardino and Luca Antonini, but Alberto Aquilani struck twice as both sides entered the break at 2-2.
Aquilani's third goal gave the Florence-based club the lead in the 57th minute, but Sebastian De Maio levelled with 13 minutes remaining.
Inter's winless start to 2014 continued on Sunday as they could only manage a 0-0 draw with rock-bottom Catania at San Siro.
The Milan-based club's first five games of the calendar year have now yielded two draws and three defeats, while a run of one Serie A win from nine has seen them slip to fifth.
Diego Milito went close in the first half for Inter, but their lack of creativity and cutting edge was nearly punished twice by Catania's Gonzalo Bergessio after the break.
Other results on Sunday saw Bologna climb out of the bottom three thanks to a last-gasp 1-1 draw at Sampdoria.
Alessandro Diamanti's injury-time penalty secured a point for Bologna, after Manolo Gabbiadini put the hosts ahead in the 62nd minute.
Livorno scored three times in the first 26 minutes in a 3-1 win over fellow strugglers Sassuolo, while Parma and Torino claimed 1-0 home triumphs against Udinese and 10-man Atalanta respectively.