London: Singer-actress Miley Cyrus is reportedly engaged to longtime boyfriend Liam Hemsworth.

The 19-year-old sparked engagement rumours by posting a picture on-line of a huge sparkler on her ring finger, as reported.

Cyrus tweeted a picture of what appears to be a large, diamond engagement ring in her finger, with a message promoting a brand of nail polish.

"They're still keeping it a big secret, but they're seriously talking marriage. Liam is crazy about her! Miley wants the whole nine yards as far as a big wedding goes," a source said.

The 'See You Again' singer met Hemsworth on the set of their 2010 film, "The Last Song", and the pair have been dating ever since.