MILAN — Napoli survived a tough test at Atalanta Sunday as Dries Mertens' second-half goal secured a 1-0 win that kept it top of Serie A.

Lazio scored five goals for the second league game in a row as it hammered Chievo 5-1 despite an injury to Serie A top-scorer Ciro Immobile and veteran Fabio Quagliarella grabbed a hat trick in Sampdoria's 3-1 win over Fiorentina.

Napoli, which avenged its home Coppa Italia defeat by Atalanta earlier this month, leads with 54 points from 21 games, four clear of Juventus.

Mertens ran on to a through ball by Jose Callejon and let the ball bounce several times before scoring with a dipping half-volley over goalkeeper Etrit Berisha in the 65th minute.

The Belgian, who had not scored in his last nine league games, took his tally for the season to 11 as his side extended its unbeaten away record in the league to 24 games.

Lazio went ahead through Luis Alberto in the 23rd minute, were pegged back by Manuel Pucciarelli's goal two minutes later and regained the lead through Sergej Milinkovic-Savic just after the half hour.

Immobile, who has scored 20 league goals this season, limped off shortly afterward.

Chievo was awarded a penalty in first-half stoppage time for a foul by Senad Lulic on Mariusz Stepinksi but the referee changed his mind after consulting the video replay system (VAR).

Milinkovic-Savic scored the third with a brilliant volley in the 68th minute before Bastos and Nani added two more in the final 10 minutes to floor the Flying Donkeys.

Quagliarella opened his account against Fiorentina after half an hour, fired home the second after 60 minutes and completed his hat trick with a close-range effort. Carlos Sanchez scored a consolation for the visitors.

Crotone won the relegation battle at Verona 3-0 and Bologna beat bottom club Benevento by the same score. Udinese was held 1-1 at home by SPAL and Torino's visit to Sassuolo ended with the same scoreline. — Reuters