Suspected racist chanting halted play at the Stadio Olimpico on Wednesday as hosts Lazio suffered a 2-0 defeat that kept visitors' Napoli's sterling Serie A season on track.

Goals by Gonzalo Higuain, the Argentine's 23rd in as many league games, and Jose Callejon combined to keep Maurizio Sarri's men top of the table with a two-point lead on champions Juventus.

But the game was marred by a three-minute suspension in the second half on the orders of match officials for racist and insulting chanting aimed at Napoli defender Kalidou Koulibaly.

Higuain is bidding to beat Gunnar Nordahl's all-time Serie A record of 35 goals in a single, 20-team season (1950) and after spurning an early chance was soon into his stride, thanks to a slice of fortune.

The Argentine ran on to Callejon's through ball on 24 minutes only to see Federico Marchetti come out to block, but as the ball bounced up Higuain chested it home.

Callejon, who hit a brace in a 5-1 thumping of Empoli last weekend, doubled Napoli's lead three minutes later.

Lazio may now face sanctions for the racist chanting.

To make matters worse, Stefano Pioli's men dropped one place to ninth, with Empoli going the other way thanks to Manuel Pucciarelli's leveller at the death in a 1-1 draw with Udinese.

Juventus had a Sebastian De Maio own-goal, from Juan Cuadrado's angled strike, to thank for a 1-0 win over Genoa and a 16th win of the campaign amid what is set to be a tough month of competition on three fronts.

However despite setting a new club record of 13 consecutive wins, coach Massimiliano Allegri looked furious when second-half substitute Simone Zaza saw red for a rash, studs-up challenge that left the Turin giants exposed for the final minutes.

Inter Milan looked to be heading up to third place after hanging on to Mauro Icardi's strike early after the restart to secure a 1-0 San Siro win over Chievo.

But Fiorentina striker Mauro Zarate, who joined the club last week from West Ham, came off the bench to hit an injury-time winner and secure a last-gasp 2-1 win for Paulo Sousa's men over Carpi after Kevin Lasagna had levelled Borja Valero's early opener for the hosts.

Fiorentina remain third to sit eight points off the pace with Inter a point further behind although Roberto Mancini was again left lamenting seeing his side spurn a host of solid scoring opportunities in a busy first half.

AC Milan's recent revival continued three days after their spectacular 3-0 derby win over Inter with a precious 2-0 win at Palermo thanks to Carlos Bacca's strike and a 33rd minute penalty from M'Baye Niang.

Roma, 2-0 winners at Sassuolo on Tuesday, are fifth at 12 points behind with Milan just two points adrift in sixth.

Their was joy at the bottom of the table, too, with struggling Verona securing their first win of the campaign after former Milan striker Giampaolo Pazzini hit an 84th minute winner in a 2-1 defeat of 10-man Atalanta.