George Clooney and his fiancee Amal Alamuddin have celebrated their engagement at a star-studded party in the US.

The smitten couple, who are set to wed after Hollywood star George popped the question last month, toasted their engagement at a Malibu restaurant, reported E! News.

The actor, 52, and the London lawyer, 36, were joined at the Cafe Habana by good friends including supermodel Cindy Crawford and her husband Rande Gerber, and U2's Bono.

Pictures online show the couple holding hands, with human rights barrister Amal showing off her seven-carat diamond ring. Both were dressed casually, with George in jeans and Amal in shorts and a top.

Meanwhile, the Daily Mirror has revealed that Gravity star George wooed Amal by email after meeting her at a fundraising event last year.

When Amal, once voted London's hottest barrister, declined to take his phone number, George apparently emailed her and said: "I think the reported hottest man in the world should meet with the hottest human rights lawyer in the world."

A friend said: "At first Amal was playing very hard to get and would not take his phone number, which simply made George even more intrigued.

"In the end he managed to get her email address and began sending her a series of flirty messages. He was very up front and joked about the fact they were both considered the hottest people in their respected professions.

"It was all very tongue in cheek but it got the ball rolling. Amal found it funny, but she still made him wait a few days before replying."

The source went on: "It was George's forward banter which ultimately got them talking.

"Once she replied that was it - it's been non-stop ever since."

The couple are rumoured to be planning to wed later this year. While they haven't announced any details of their big day, there is speculation they will exchange vows at George's home at Lake Como in Italy.