The World Cup kicks off with host nation Qatar facing Ecuador on Sunday as the month-long football showpiece finally gets under way after a tortuous 12-year build-up dogged by off-field controversies.

Foreign government officials, VIPs and celebrities were in the crowd as the first World Cup staged in the Arab world opens at the Bedouin tent-inspired Al Bayt Stadium in Al Khor, 50 kilometres (31 miles) outside of Doha.

The venue is one of an array of new stadiums built for the tournament, which has cost Qatar an estimated $200 billion, the most expensive World Cup in history.

South Korean K-pop star Jung Kook headlined the 30-minute opening ceremony, which organisers said Sunday reflected themes of "humanity, respect and inclusion".

The list of foreign dignitaries at Sunday's opening included Saudi Arabia's powerful Crown Prince Mohammed bin Salman, who orchestrated a regional blockade of Qatar in 2017.

World Cup organisers hope the start of the football will quell the controversies that have overshadowed preparations for the tournament ever since Qatar was named as host nation in a shock FIFA vote in 2010.

Qatar's treatment of migrant workers and the Gulf state's human rights record have dominated the pre-tournament headlines.

On Saturday, FIFA president Gianni Infantino went on the offensive in an aggressive rebuttal of the opprobrium aimed at the event, arguing that much of the criticism was unfair.

"This moral lesson-giving — one-sided — is just hypocrisy," Infantino said.

"I don't want to give you any lessons of life, but what is going on here is profoundly, profoundly unjust."

Controversies look certain to rumble on into the tournament even after the action starts.

Several European nations taking part — including England, Germany and Denmark — have said their players will wear rainbow-coloured "OneLove" armbands in a gesture of solidarity with gender minorities.

The move raises the prospect of disciplinary action from FIFA, which has revealed plans to make its own alternative armbands available to teams.

Infantino insisted that all World Cup visitors would be welcome regardless of sexual orientation.

"I've been speaking about this topic with the highest leadership," he said. "They can confirm that I can confirm that everyone is welcome."

Benzema blow, Brazil arrive

All 32 teams competing at the World Cup have now arrived, with five-time champions Brazil the last to touch down in Doha late on Saturday.

Defending champions France suffered another injury hammer blow early Sunday after confirmation that star striker and Ballon D'Or winner Karim Benzema had been forced out of the tournament with injury.

The Real Madrid star limped out of a training session at the French camp on Saturday evening with a left thigh injury.

The French federation later confirmed in a statement that the 34-year-old would require "a recovery period of three weeks" and would play no part in the competition.

"I am extremely sad for Karim, for whom this World Cup was a major objective," said France coach Didier Deschamps, who has decided not to replace the forward.

"Despite this new blow for the France team I have full faith in my squad. We will do all we can to rise to the huge challenge that awaits us."

Benzema's withdrawal comes with France already battling the injury absence of star midfielders Paul Pogba and N'Golo Kante.

Belgium are also reeling from an injury blow after striker Romelu Lukaku was ruled out of the Red Devils' opening two games as he continues to recover from a hamstring problem.

Australia winger Martin Boyle joined the list of footballers who will play no part in the tournament. Head coach Graham Arnold said the winger had failed to recover from a knee injury.

"We all feel for Martin and it is a cruel blow for him," Arnold said.