Demi Lovato's engagement ring reportedly cost between £2 million and £4 million.

Actor Max Ehrich, 29, proposed to the 27-year-old singer last week, less than five months after they first started dating, with a ring designed by Peter Marco, which is believed to be between 10 and 20 carats.

A source told TMZ that the ''diamond is an emerald cut that was hand set in platinum, and flanked on all sides by smaller trapezoid-shaped diamonds designs'' and it is worth anywhere from £2 million to £4 million.

Meanwhile, in her engagement announcement, Demi gushed that she knew she loved Max ''the moment'' they met.

She wrote on Instagram: ''When I was a little girl, my birth dad always called me his 'little partner' - something that might've sounded strange without his southern cowboy like accent.

''To me it made perfect sense. And today that word makes perfect sense again but today I'm officially going to be someone else's partner.''

She added: ''@maxehrich - I knew I loved you the moment I met you.

''It was something I can't describe to anyone who hasn't experienced it firsthand but luckily you did too.. I've never felt so unconditionally loved by someone in my life (other than my parents) flaws and all. You never pressure me to be anything other than myself. And you make me want to be the best version of myself. I'm honored to accept your hand in marriage. I love you more than a caption could express but I'm ecstatic to start a family and life with you. I love you forever my baby. My partner. Here's to our future!!!! (sic)''

And he wrote: ''Ahhhh. You are every love song, every film, every lyric, every poem, everything I could ever dream of and then some in a partner in life. Words cannot express how infinitely in love with you I am forever and always and then some. I cannot spend another second of my time here on Earth without the miracle of having you as my wife. here's to forever baby ahhhhhhhhhhhhhhhhhhh jeuejfjqjweuvu I'm so excited you are the most beautiful inside and out in the entire world & I couldn't be more grateful God brought us together I LOVE YOU SO MUCH @ddlovato AND WILL FOREVER CHERISH YOUR PURE, BEAUTIFUL, INFINITE SOUL (sic)''