Robert Lewandowski scored just his second LaLiga goal since October as Barcelona beat Cadiz 2-0 to restore their eight-point lead over Real Madrid.

The 34-year-old added to Sergi Roberto's opener as two goals late in the first half undid a Cadiz side who held their own for much of the Camp Nou clash and had two goals from Roger disallowed.

Another clean sheet, Barcelona's 17th shutout in LaLiga this season, puts Xavi's side a step nearer the title, and this was a seventh consecutive league victory, the third time they have had such a run under the leadership of their former midfielder.

It sealed a double for the season, too, with Barcelona having won 4-0 in September against the team who are now fighting a relegation battle, sitting just two points outside the bottom three.

Cadiz thought they had made a 19th-minute breakthrough when a delicious pass over the top from Santiago Arzamendia, with the outside of his left boot, found Roger. The striker finished well but had strayed a foot offside, to Barcelona's relief.

Lacking service, Lewandowski barely had a sniff of goal until the 41st minute, when a cross from Ferran Torres on the right looked ideal for him to nod in at the far post. Under pressure, though, he could not make a clean connection.

The same combination combined as Barcelona struck two minutes later. Lewandowski's stooping header from Torres' clipped cross was kicked off the line by Isaac Carcelen but only as far as Sergi Roberto, who slammed it back into the back of the net from eight yards.

Lewandowski drove in Barcelona's second goal in stoppage time, a clinical low strike from 16 yards taking his haul to 15 in the league this season.

The former Bayern Munich striker prodded a shot against the top of the bar early in the second half, before Cadiz's Roger had a second goal disallowed after finishing well from a corner, with team-mate Fali penalised for a nudge into Marc-Andre ter Stegen.

The visitors perhaps had reason to feel aggrieved, and Cadiz kept pushing, with Ter Stegen saving well from substitutes Fede San Emeterio and Chris Ramos late in the game, before Anthony Lozano headed against the left post. It wasn't to be their night.