Robert Lewandowski scored twice as La Liga champions Barcelona wrapped up their domestic treble-winning season with a comfortable victory at Athletic Club.

Having sealed their 28th league title with two games to spare, Hansi Flick's men scored their 100th goal of the league campaign with the 14th-minute opener.

Lewandowski expertly chipped home goalkeeper Unai Simon, before he doubled the lead only three minutes later, arriving at the back post to head home following Raphinha's inswinging corner.

The goals were his 27th in the league and 40th overall this season.

Substitute Dani Olmo sealed the victory from the penalty spot in the fourth minute of added time as Barca finished the campaign with 88 points from 28 wins and four draws.

They finished four clear of Real Madrid as German Flick won the La Liga, Copa del Rey and Spanish Super Cup titles during his first season in charge of Barca.

Despite his side's first-half dominance, Athletic Club had two good chances to reduce the deficit before the break - both falling to Maroan Sannadi, who should have done better.

The 24-year-old striker failed to hit the target from six yards out after getting on the end of Unai Nunez's cross.

Sannadi then poked wide with only visiting goalkeeper Inaki Pena to beat after being played through on goal by his captain Oscar de Marcos, who was making his 570th and final appearance for the Bilbao outfit.

Lewandowski, who has only Real Madrid's Kylian Mbappe (31) ahead of him in the La Liga scoring charts this season, passed up chances to complete his hat-trick early in the second half.

Athletic Club went close again when Barca centre-back Pau Cubarsi's defensive header from Alex Berenguer's free-kick rattled the crossbar.

De Marcos received a standing ovation from the San Mames crowd as he was substituted in the 89th minute, passing the captain's armband to future captain Inaki Williams.

But it was Barca who had the last word as Olmo scored from the spot in the stoppage time after he was brought down in the box by Yuri Berchiche.

The hosts, who had secured their Champions League qualification before the final day, finished fourth, level on 70 points with fifth-placed Villarreal.