Qatar became the first home team to lose their opening World Cup match as Ecuador cruised to a 2-0 victory over the hosts, with Enner Valencia scoring twice in the tournament curtain-raiser on Sunday.

Asian champions Qatar enjoyed the backing of the majority of the crowd at the 60,000-capacity Al Bayt Stadium, but could not follow a glitzy opening ceremony with a statement performance.

Ecuador thought they had made a dream start when they silenced the home fans as Valencia headed in, only for the goal to be ruled out by VAR for an offside in the build-up.

Valencia did break the deadlock with a penalty in the 16th minute and doubled his tally just after the half-hour mark.

Qatar improved slightly in the second period, but by the end of the 90 minutes, the excitement which greeted the build-up -- featuring Morgan Freeman and BTS star Jung Kook -- was a distant memory as thousands of fans left early amid a deflated atmosphere.

Felix Sanchez's Qatar will likely need a positive result in their second Group A match against Senegal on Friday just to avoid the ignominy of becoming only the second hosts, after South Africa in 2010, to be dumped out in the first round.

Hopes were high among the crowd that Qatar could make a winning start, but the deficiencies of the World Cup debutants were ruthlessly exposed by an impressive Ecuador.

Qatar failed to even muster a shot on target in the game, with spectators filing out of the stands long before the final whistle.

In the 92-year history of the tournament, home countries had previously won 16 and drawn six of their opening matches.

The South Americans had the ball in the net inside three minutes when captain Valencia nodded home from Felix Torres' miscued overhead kick.

VAR officials spotted an offside against Michael Estrada in the build-up after Torres challenged for the ball with Qatar goalkeeper Saad Al Sheeb.

Ecuador were completely dominant in the early exchanges, though, and were awarded a penalty after Valencia was tripped by Al Sheeb when through on goal.

The former West Ham forward coolly sent Al Sheeb the wrong way from the spot and stroked the ball into the bottom corner to score his 36th international goal.

Ecuador did not have to wait long to double their advantage as, after a surging run from Moises Caicedo, right-back Angelo Preciado swung in a cross which Valencia met with a thumping header.

Even the small section of noticeably enthusiastic Qatari fans situated behind the goal, who arrived together after the majority of the crowd and wore matching t-shirts, briefly fell silent.