Adam Levine and Behati Prinsloo

Adam Levine and Behati Prinsloo

Adam Levine informed ex-girlfriend Nina Agdal of his engagement via text message.

The Maroon 5 singer - who announced he will marry Victoria's Secret babe Behati Prinsloo last week - left the model "heartbroken" after she learned of his impending nuptials through an impersonal note, according to the New York Post newspaper.

Adam, 34, briefly dated the 21-year-old beauty earlier this year after he and Behati ended their one-year romance in May.

'The Voice' USA coach was spotted on holiday with Nina in Los Cabos, Mexico, in June, but quickly reunited with Behati following the getaway after realising he still had feelings for the Namibian model.

Adam was reportedly not "serious" about his relationship with Nina and decided to win Behati back.

A source said: "The Nina thing was not that serious and was not going to last. After Adam broke up with Behati, he couldn't stop thinking about her. He knew he really loved her and wanted to be with her."

The singer's 24-year-old fiancée recently said she was "so happy" about becoming the future Mrs. Levine and revealed that Adam proposed on a traditional bended knee.

She said: "I am so happy and excited and still can't believe it's true! It was a one-knee thing! It was serious, it was very old school!"

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