Atletico Madrid was made to suffer before claiming a 3-1 win at home over Belgian side Union Saint-Gilloise in the Champions League on Tuesday night.

Julian Alvarez opened the scoring for Atletico in the 39th minute after excellent work from Giuliano Simeone, who opened up space down the right for Atletico, before feeding the ball to his Argentine teammate.

Antoine Griezmann saw a goal ruled out in first-half injury time as he followed in to slide home after Nahuel Molina had hit the crossbar, but Conor Gallagher doubled Atletico's lead in the 78th minute following a powerful run from Alexander Sorloth.

Although Atletico had a comfortable lead, Union SG players never let their heads drop and Ross Sykes got them back into the game with a powerful header.

The game was suddenly more open with both sides finding space on the break. Union SG goalkeeper Kjell Scherpen made a fine save to deny Alvarez his second goal, while at the other end Louis Patris could have levelled with a header, but his effort into the ground took the sting off the ball and allowed Jan Oblak an easy save.

Marcos Llorente added Atletico's third with a simple finish in the last minute of injury time after Scherpen had denied Sorloth, but could do nothing to block the rebound.

The win leaves Atletico with six points from its four group matches to date, while Union SG remains on three.