MILAN (AP) " Inter Milan coach Stefano Piolo warned Serie A his team was yet to peak after it beat bottom club Pescara 3-0 for its ninth successive victory in all competitions on Saturday.
Danilo D'Ambrosio, Joao Mario, and Eder scored for Inter to jump above Lazio and into fourth place, two points below Napoli and three below Roma. Napoli hosts Palermo on Sunday, a few hours after Roma plays at Sampdoria.
League-leading Juventus, which visits Sassuolo, is a point above Roma.
Inter visits Juventus next weekend, after the Italian Cup quarterfinal at home to Lazio on Tuesday.
"Many players are giving a lot but they can still do even more: We haven't got to our peak," Pioli said.
"We know that the game against Juventus will be important for our position in the league, but first there's the Italian Cup ... against a great team like Lazio, in a competition we really care about. Our focus has to be entirely on the next match, then we will think about Juve."
Inter dominated but had to survive an early scare before taking the lead in the 23rd minute.
Grigoris Kastanos, who is on loan from Juventus, almost scored on his Serie A debut but Inter goalkeeper Samir Handanovic parried the teenager's effort. Valerio Verre fired in the rebound but it was ruled out for offside.
Moments later, Albano Bizzarri tipped Joao Mario's angled drive around his right post and the resulting corner was taken short, allowing Marcelo Brozovic to whip in a cross which was volleyed into the bottom right corner by D'Ambrosio from close range.
Inter doubled its lead two minutes before the break in a move started and finished by Joao Mario, who prodded in Ivan Perisic's low cross.
Inter sealed the match in the 73rd although Icardi looked offside when he ran onto Brozovic's through ball and pulled back for substitute Eder to side-foot home.
LAZIO 0, CHIEVO VERONA 1
Lazio's hopes of qualifying for the Champions League took a blow as it conceded a last-gasp goal at home to Chievo Verona, whose goalkeeper Stefano Sorrentino was in imperious form.
Sorrentino denied Marco Parolo on numerous occasions, as well as Sergej Milinkovic-Savic and Lucas Biglia.
"That's football, it's cruel," Lazio coach Simone Inzaghi said. "We had 15 chances and if you don't score then invariably you concede in the 90th, with their first chance."
Lazio also missed suspended striker Ciro Immobile, who netted three goals in his last four matches.
Just as it appeared as though the match was heading for a goalless draw, Chievo counterattacked and Massimo Gobbi pulled back from the byline for Roberto Inglese to fire home in the 90th minute.
Lazio slipped to fifth, two points behind Inter and four below third-placed Napoli.
There was an ugly incident at the end of the match as Biglia had to be held back by Lazio staff after being verbally abused and spat at by a Lazio fan. Teammate Mamadou Tounkara was in the stands and also had to be held back as he appeared to try to punch the supporter.
Biglia's wife was in the same sector.
"There was a squabble, everyone is entitled to their own opinion," Parolo said. "But I don't think you can say anything about tonight, and even less to someone like Biglia, who apart from being our captain, is someone who always gives his all. We are with him."
The police were investigating but the club was unlikely to take any action against Biglia.
"Biglia is our captain, he is an exceptional lad, with outstanding skills," Lazio club manager Angelo Peruzzi said. "I'm sorry that some so-called fan attacked him. That shouldn't happen at all ... Biglia is our captain, he will remain our captain, because all the squad follows him."
Tounkara apologized on social media.