Doha (AFP) - Saudi Arabia pulled off one of the greatest upsets in World Cup history on Tuesday, roaring back to beat Argentina 2-1 – a result described by Lionel Messi as a “heavy blow”.

Copa America champions Argentina came into the match in Qatar on a 36-match unbeaten streak and appeared to be on their way to a straightforward victory after Messi stroked home an early penalty.

Lionel Scaloni’s team could have put the game beyond Saudi Arabia’s reach in the first half but had three goals chalked off for offside.

Saudi Arabia, ranked a lowly 51st in the world, equalised early in the second half through Saleh Al-Shehri, silencing the hordes of Argentina fans.

And just minutes later the Green Falcons were in front when Salem Al-Dawsari rifled an unstoppable shot into the top corner after a delightful piece of trickery.

Argentina laid siege to the Saudi goal as the minutes ticked down but goalkeeper Mohammed Al-Owais proved unbeatable and the final whistle sparked scenes of jubilation.

“It’s a very heavy blow, a defeat that hurts, but we must continue to have confidence in ourselves,” said Messi, who has never won the World Cup in his illustrious career.

“This group is not going to give up. We will try to beat Mexico.”

Saudi’s French coach Herve Renard said the “stars were aligned” for his team.

“We made history for football,” he added. “It will stay forever, this is most important. But we also have to think about looking forward. We still have two difficult games before us.”

Defeat is a bitter blow for Argentina, who were one game away from equalling Italy’s all-time record of 37 matches unbeaten.

Argentina coach Scaloni insisted his team had not taken their opponents lightly.

“What comes ahead is to rise up, to face Mexico,” he said. “They will be tough, as everyone is at the World Cup. Now we need to win two games to move on.

“Of course this is difficult but regardless of the result today we would anyway try to win all the games.”

The other match in Group C, later on Tuesday, pits Robert Lewandowski’s Poland against Mexico, with the Barcelona forward still seeking his first World Cup goal.

- Mbappe the difference -

Messi’s PSG teammate, Kylian Mbappe, is already a world champion at the age of 23.

The forward will be licking his lips ahead of France’s Group D match against an Australia side desperately lacking star power.

France coach Didier Deschamps is without first-choice midfielders Paul Pogba and N’Golo Kante for the whole tournament while Ballon d’Or winner Karim Benzema has also been ruled out.

Mbappe will lead a French attack in which veteran Olivier Giroud is expected to feature.

Denmark drew 0-0 with Tunisia in the other match in the group on Tuesday, with talisman Christian Eriksen appearing in his first match in a major tournament since suffering a cardiac arrest during the European Championship last year.

Saudi Arabia’s dramatic win has shifted the focus to action on the pitch but off-field politics is still making headlines.

Belgium’s Jan Vertonghen said he was “afraid” to talk about human rights after European nations decided not to wear a rainbow-themed captain’s armband.

Seven countries, including England and Germany, abandoned plans to wear the armbands in Qatar because of the threat of FIFA disciplinary action, including bookings.

They had been viewed as a symbolic protest against laws in the host nation, where homosexuality is illegal.

“I’m afraid if I say something about this I might not be able to play tomorrow,” the defender said.

“It’s an experience I’ve never felt in football before. I feel controlled. I’m afraid to even say something about this.”

Germany’s football association said it was examining if FIFA’s threat to impose disciplinary action was legal.