Watch Lady Gaga's surprise cover of John Lennon song in front of thousands

Pop star Lady Gaga sang John Lennon's 'Imagine' sitting at a flower-covered piano as the inaugural European Games got off to a glamorous start in the Azeri capital with a dazzling opening ceremony on Friday.

Pop star Lady Gaga surprised thousands of fans who had turned up for the glamourous opening ceremony of the inaugural Europen Games with a dazzling performance of John Lennon's Imagine on a flower-covered piano.

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The American six-time Grammy Award winner was a surprise addition to the ceremony, aimed at setting the stage for 16 days of competition in the continent's first multi-sports event which Azerbaijan hopes will put it firmly on the global sports map.

Watch the performance here

In a two-hour curtain-raiser produced by Dimitris Papaioannou, who was in charge of the Athens 2004 Olympics ceremonies, the history of the nation on the shores of the Caspian sea unfurled in a kaleidoscope of colours and sounds.

"This is the proudest moment in the history of the European Olympic Committees," EOC President Patrick Hickey, whose organisation awarded the Games to Baku in 2012, said in a brief speech.

"We are creating a landmark moment in European sport. Tonight we add the missing fifth ring to the continental Games of the world." The 6,000 athletes entered the stadium with Azeri President Ilham Aliyev watching from the stands, along with Russian President Vladimir Putin, sitting next to International Olympic Committee President Thomas Bach, and 35 other heads of state.

A wide security cordon was thrown around the stadium and the surrounding area hours before the ceremony started.

The energy-rich nation has spent well over a billion dollars to stage its biggest sports extravaganza to date, building several venues from scratch for the 16-day competition.

And here's the original John Lennon song