Thousands of empty seats told the sad story as Qatar's long-awaited World Cup debut ended in a bad case of stage fright on Sunday.

Long before the final whistle at the spectacular Bedouin tent-inspired Al Bayt Stadium, the host nation's fans among the 67,372 crowd had started heading for the exits.

The exodus began soon after Ecuador striker Enner Valencia headed his second goal shortly after the half-hour mark against the outclassed World Cup hosts.

As the second half wore on, swathes of unfilled seats could be seen throughout the arena as an evening that began with joyous celebrations and heady optimism ended with a whimper.

The downbeat finale was in stark contrast to the mood in the hours before kick-off at the stadium in Al Khor, 50 kilometres (31 miles) north of Qatar's capital Doha.

Thousands of people arrived at the vast Lusail train station where the subway line built especially for this tournament at a cost of $36 billion ends and spectators boarded a fleet of buses for the final leg of their journey.

The security forces appeared tense, aware that the eyes of the world are on this Gulf state, which many critics say should never have been awarded the World Cup.

Once the spectators arrived at the spectacular venue, camels and horses lined the road to the turnstiles.

Carlos Alvear, an Ecuadoran who lives in Ecuador, said: "It's really special to be here. It's the first World Cup in the Middle East, it's historic and Ecuador is here for the opening match.

"To be honest, it's all a bit bizarre. It's pretty quiet, even if there are more Ecuadorans than I thought there would be. But all these buildings look pretty empty."

- 'Trust in our team' -

For a Qatari supporter who gave his name only as Abdallah, it was an exciting moment.

"We have been waiting for this moment for 12 years," he said. "We have every confidence for this festival.... We trust in our team. We have ambition but are realistic."

He was confident of victory against the South Americans and predicted his team would be runners-up in their group and go through to the next round -- where England could await.

"Today we will win, but we will be second behind the Netherlands. Then against England, we will win," he said with a smile.

Danny, a supporter from the English city of Norwich, said he planned to "jump on the bandwagon today" and support Qatar.

His friend who gave his name only as Abdul, from Sheffield in northern England, had brought a Qatari flag and was wearing a red top under his England shirt in case Qatar scored.

Danny was staying in the shipping container accommodation set up for visiting supporters for two weeks and said it "isn't quite what he was expecting".

Away from the opening match, thousands of Mexican and Argentine fans thronged the Corniche seafront promenade in the centre of Doha.

Leopold Fes, a 65-year-old Belgian, said he was finding it difficult to accept the last-minute decision to ban the sale of alcohol at stadiums in the strict Islamic state.

"I don't think it will be like other World Cups," he said. "No alcohol makes it strange. Football and alcohol go together for a lot of people."