Cristiano Ronaldo became the fastest player to 50 Serie A goals as Juventus put themselves on the cusp of a ninth successive Scudetto with a 2-1 win over Lazio.

Juve went into Monday's clash with the chance to go eight points clear at the top with four games to go after both Inter and Atalanta dropped points over the weekend.

They made no mistake against a Lazio side that has seen their title challenge fade badly since the restart, Ronaldo scoring twice in the space of three second-half minutes to secure victory.

A 51st-minute penalty took him to his half-century in 61 matches and had an easy finish for a second that looked to have ended the game as a contest until Ciro Immobile's penalty set up a tense finale that Juve survived to all but ensure the title will remain in Turin.

Alex Sandro, who rescued Juve in their 3-3 draw with Sassuolo last time out, headed against the post from Matthijs de Ligt's cross in the 11th minute.

However, Thomas Strakosha was not legitimately tested until the 35th minute when he turned Adrien Rabiot's effort over after a surging run from the Frenchman, with Ronaldo heading wide from the resulting corner.

Lazio were also denied by the woodwork shortly before half-time when Immobile sent a rasping strike cannoning off the post.

Ronaldo attempted to prod over the line on the rebound after Strakosha thwarted Dybala following quick feet in the box from the Argentina forward, only for a goalmouth clearance to maintain parity.

But there was no denying Ronaldo his place in Serie A history after VAR overturned the decision that Bastos had handled his shot outside the area.

Strakosha correctly dove to his left but did not get a touch to a typically confident penalty and he was similarly helpless as Dybala won possession in midfield and surged through on goal before laying the ball off for Ronaldo to tap into an empty net.

Ronaldo clattered the crossbar with a header after a cross from Dybala, who again found Strakosha in fine form to keep out another close-range effort.

Leonardo Bonucci paid the price for nonchalant defending as he felled Immobile, who won and emphatically converted an 83rd-minute finish to fray Juve nerves.

The hosts were grateful to a flying save from Wojciech Szczesny to keep out Sergej Milinkovic-Savic's free-kick, but they held firm and the title now appears a formality for Maurizio Sarri's men.