Milan trail Juve by a point at the top but the leaders have a game after their match at Parma on Tuesday night was called off due to snow.
Third-placed Udinese took advantage to cut the gap to three points with a 2-1 win at home to Lecce while fourth-placed Lazio are now just two points behind after their fine win.
Milan's match in the capital saw them force the early pace but in the second half Lazio came more into the match and 14 minutes from time Hernanes was put through and he hooked the ball home.
Tommaso Rocchi's late second sealed the three points for Lazio to boost their title hopes.
Diego Milito scored all four Inter goals at the San Siro, but his team could not seal the three points as Fabrizio Miccoli grabbed a hat-trick for the visitors.
The snow-covered pitch made for an exciting game and Milito twice put them ahead in the second half only for Josip Ilicic to play in Miccoli to complete his treble and equalize for the final time.
In the Copa del Rey, Barcelona were held 1-1 at Valencia in their semifinal first leg tie in the Mestalla.
Lionel Messi had a penalty saved after Carlos Puyol had leveled Jonas' opener for the hosts. Valencia went ahead in the 27th minute when Jeremy Mathieu pulled the ball back for Jonas to sidefoot home.
But defender Puyol headed Barcelona level in the 35th minute. Messi's penalty miss came after 56 minutes as Alvez pushed his shot away.
Barca substitute Dani Alves hit the post but they could not find a winner.
In the English Premier League, Newcastle moved up to fifth spot and kept up their challenge for Champions League football with a 2-0 win at struggling Blackburn.
Ryan Taylor's shot took a huge deflection off Scott Dann to put Newcastle ahead before the home side created a deluge of chances to level.
Danny Simpson cleared off the line and Leon Best headed against his own bar before David Dunn saw his penalty saved by Tim Krul in the visiting goal.
Blackburn continued to press in the second half before Gabriel Obertan scored a late second.
They took advantage of Arsenal's disappointing 0-0 draw at Bolton where Robin van Persie came closest to scoring with a superb effort which struck the woodwork.
Djibril Cisse scored on his debut for Queens Park Rangers, but after his side took a two-goal lead home team Aston Villa deservedly hit back to claim a 2-2 draw at Villa Park.
Sunderland's fine run under Martin O'Neill continued with a fine 3-0 home win over Norwich with Frazier Campbell setting them on their way with a stunning opener.