George Clooney and fiancée Amal Alamuddin celebrate their engagement at Bono's birthday party

Newly-engaged couple George Clooney and Amal Alamuddin had plenty of reason to celebrate on Sunday as they attended Bono’s star-studded birthday party.

The loved-up pair arrived hand-in-hand for the Malibu event held at Café Habbana, where they were joined by the likes of Cindy Crawford and her husband, Rande Gerber, who owns the restaurant.

The famous group gathered on the back patio, where they toasted the future bride-and-groom with tequila and wine.

George Clooney and fiancée Amal Alamuddin were spotted together at Bono’s birthday bash

After the toast, George and his fiancée were all over each other,” a source told People. “Lots of hugging.”

Smiling Amal could be seen showing off her impressive seven-carat diamond engagement ring as she chatted with her husband-to-be’s close friends.

There was even a bit of karaoke; Bono got up and sang during the party, as did supermodel Cindy, who reportedly duetted with her daughter Kaia.

Rande Gerber and Cindy Crawford were also seen at the party

An eyewitness told E! News that the venue was busy with people celebrating Mother’s Day. “They got a show they didn’t expect and other (restaurant patrons) said it was the best Mother’s Day ever.”

George, 53, proposed to British human rights lawyer Amal, 36, in late April, after seven months of dating.

The future Mr and Mrs Clooney recently returned from a holiday in Cabo, Mexico, where they celebrated a friend’s wedding. “You can tell these two are in love,” an onlooker said.

Don't miss a beat with HELLO! Canada's Daily Hits newsletter, your daily dose of royal and celebrity news, fashion, weddings and more. CLICK HERE to sign up for free!