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Nana Mouskouri performs Wednesday at the restored ancient stone theatre Odeon of Herodes Atticus in Athens. Her final concert was Thursday. (Losmi Chobi/Associated Press)

Nana Mouskouri took her last bow after 50 years in music Thursday with a farewell concert in her native Greece.

An estimated audience of 10,000 people filled the ancient Odeon of Horodes Atticus at the foot of the Acropolis in Athens to hear her final concert.

Mouskouri, 73, announced her plans to retire three years ago and has completed a worldwide tour.

"I have been known to sing in a certain way and my fear is to lose this way of singing which will disappoint a lot of people," said Mouskouri, explaining her retirement to Reuters.

"It's not that I abandon singing or that I will never sing again in my life anywhere now, but I will not go on tours anymore. I don't want to have this fear all the time when you go on stage, this stage fright."

On Wednesday, in the first of two concerts in Athens, Mouskouri wore her trademark black glasses and a red dress and sang from her wide repertoire.

Mouskouri has sold more than 300 million records worldwide, and is one of the world's best-selling artists.

Born in Crete, she sings in French, English, German, Greek, Spanish, Italian, Dutch, Portuguese, Hebrew and Japanese, her record company Universal says.

Mouskouri trained as a singer in Athens and sang in her first Greek music festival at 25.

Since then she has recorded 1,500 songs and toured with artists such as Harry Belafonte.

Her life has been a "fairy tale," she said, and the farewell tour was a way to express her gratitude to her legions of fans.

"This tour was the opportunity to say thank you to the people," she said.

"I wouldn't really go without saying thank you because, thanks to the audience, I have been around for so many years because they listen to me."

Mouskouri, who has been a goodwill ambassador for UNICEF, said she now wants to involve herself more closely with humanitarian causes. She may also mentor young singers.