Cristiano Ronaldo's double in a 2-1 win against Sampdoria helped Juventus set a new Serie A record for most points registered in the first half of a season.

Ronaldo gave the defending champions an early lead and after Fabio Quagliarella had equalised with a first-half penalty, the Portuguese converted a controversial spot-kick himself in the 65th minute.

That effort was Juve's 100th goal in 2018 in all competitions, while both penalties were awarded for handballs after referee Paolo Valeri had consulted with the video assistant referee.

Sampdoria thought they had drawn level in stoppage time through substitute Riccardo Saponara, only for his effort to be ruled out for offside after Valeri had again checked the replay.

Juve, chasing their eighth successive league title, extended their unbeaten league start to 19 matches and have dropped only four points in the process.

Napoli bounced back to winning ways after their Boxing Day defeat at Inter Milan thanks to Dries Mertens' late strike in a 3-2 home win against Bologna.

Arkadiusz Milik had given Napoli the lead in both halves, but Bologna hit back twice through Federico Santander and Danilo before Mertens' arrowed home an 88th-minute winner.

Keita Balde's second-half strike secured Inter a hard-fought 1-0 win at lowly Empoli, while Sergej Milinkovic-Savic lashed home a second-half equaliser for Lazio, who were held 1-1 at home against Torino.

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Milinkovic-Savic's bullet just after the hour-mark rescued Lazio a point after Torino striker Andrea Belotti had converted a penalty in first-half stoppage time.

Lazio defender Adam Marusic and Torino midfielder Soualiho Meite were both sent off for arguing with the referee late in the game.

Gonzalo Higuain fired AC Milan's winner as they came back from behind to beat SPAL 2-1 at home.

Samu Castillejo equalised for Milan soon after Andrea Petagna had given SPAL a 13th-minute lead and Higuain struck the winner midway through the second half.

Milan goalkeeper Gianluigi Donnarumma made two fine stoppage-time saves to deny SPAL shortly after team-mate Suso had been dismissed for his second bookable offence.

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Roma clinched back-to-back victories after a 2-0 win at Parma, where Bryan Cristante and Cengiz Under both scored second-half goals.

Sassuolo were thrashed 6-2 at home by Atalanta, for whom Josip Ilicic scored a second-half hat-trick.

Atalanta led 2-0 at the break through Duvan Zapata and Alejandro Gomez and although Alfred Duncan pulled one back for the hosts early in the second half, Gianluca Mancini added the visitors' third.

Ghana international Duncan crashed home his second soon after, but Slovenia midfielder Ilicic scored three times in the final 16 minutes.

Bottom club Chievo registered their first league win of the season thanks to Emanuele Giaccherini's second-half free-kick in a 1-0 win against relegation rivals Frosinone.

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Second-bottom Frosinone defender Marco Capuano was sent off for his second yellow card early in the second half.

Genoa were held 0-0 by Fiorentina at the Luigi Ferraris Stadium, while Ignacio Pussetto and Valon Behrami scored in either half as 10-man Udinese beat Cagliari 2-0 at home.

Udinese midfielder Rolando Mandragora was shown a straight red card after his 79th-minute challenge on Albert Cerri had been referred to the video assistant referee.