BRUSSELS, Sept 4 (Reuters) - Belgium delivered a performance of character and proved they were building "a winning team", coach Roberto Martinez said after they became the first country to qualify from the European preliminaries for next year's World Cup finals in Russia.

A 2-1 away win against Greece on Sunday ensured top place in Group H for the Belgians and a second successive World Cup finals appearance after a quarter-final finish in Brazil in 2014.

Sunday's result also extended their unbeaten run to 11 games, tying the country's previous best.

"We must be proud about being the first from Europe to qualify and now look to work harder to become better," said Martinez after the Belgians advanced to an unassailable 22 points, eight ahead of second placed Bosnia with two rounds left to play.

"It was clear that we didn't play well, we weren't ourselves. But the game was only about winning, it was like a cup final. It was not about playing good football. We had to win, in whatever manner we could. The first half of the game was probably the worst football we've played in this campaign."

Goals after half-time from Jan Vertonghen and Romelu Lukaku ensured the victory.

"I was really proud with the way the players fought. There were a few that really stood up - (Thibaut) Courtois, (Kevin) de Bruyne, Vertonghen, (Marouane) Fellaini. It is a real team and I can only but be proud of them," the coach added.

"The players were not pleased at half-time and from their reaction you can see we are creating a winning team. They showed character, inspired one another and wanted to win. In a few weeks no one will remember how we did it."

Sunday's win meant Belgium have won seven of their eight group games with a home draw against the Greeks in March the only blemish.

Belgium's 35-goal haul in eight matches is the most by any team in the 2018 European qualifiers.

(Reporting by Mark Gleeson; Editing by Sudipto Ganguly) ((mark.gleeson@thomsonreuters.com)(+27828257807)(Reuters Messaging: Reuters Messaging: mark.gleeson.thomsonreuters.com@reuters.net))