Reuters/Venice

The world's most famous bachelor, George Clooney, welcomed more A-list stars to Venice on Saturday for his wedding to human rights lawyer Amal Alamuddin, with details of the long weekend bash kept as hazy as the morning fog over the Grand Canal.

The extravaganza, billed as the party of the year, was making the Italian city of gondolas and palazzos look like Hollywood on the Adriatic.

Actors Matt Damon and Ellen Barkin, model Cindy Crawford,  Vogue editor Anna Wintour and others descended on Venice on Friday along with Clooney and Alamuddin, cruising the canals on speedboats that took them from one luxury hotel to another.

Singer Bono arrived on Saturday and other stars were expected ahead of a gala dinner on Saturday night.

Damon, wearing a tuxedo, Crawford and other guests were seen on the terrace of the famed Cipriani Hotel at a pre-gala reception before they moved to another hotel for the main party at the seven-star Aman Canal Grande Venice, housed in the 16th-century Palazzo Papadopoli on the Grand Canal.

Clooney helped guests onto the water taxis at the Cipriani and off when they reached the Aman, where workers put up a brown canvas canopy with side walls on a floating wharf to protect the guests from prying eyes and photographers' long lenses.

They were due to have drinks in a rear garden before dinner in the main dining room, where the two were were to exchange vows informally ahead of a civil service on Monday, according to local reports.

Locals and tourists didn't seem to mind if only some of those rumoured to be coming would arrive, thrilled to be part of one of the memorable days in the city's long history of hosting stars for its famous film festival, the world's oldest.

"I thought he was like the world's most eligible bachelor so I didn't realise he was ever going to get married, but I guess if you're going to get married what better spot than a beautiful Italian city like Venice?" said Canadian tourist Philip De Vooght.

A slick, wooden speedboat, appropriately called "Amore", brought the couple into the city on Friday with a retinue of boats, a modern-day version of the ceremonial entrances of the  Doges of the Venetian Republic, which lasted from the late seventh century until 1797.

Alamuddin, 36, wore a black-and-white striped dress as she arrived with Clooney on the speedboat on Friday afternoon. She changed into a more formal red dress with black butterfly patterns for a party in her honour on Friday night.

SPEEDBOAT FLEET

Guests were being ferried around the city in speedboats marked with "AG", for Amal and George.

The Kentucky-born Clooney, the two-time Oscar winner who shot to stardom in the television series "ER", had vowed never to remarry after his 1993 divorce from actress Talia Balsam.

Such was his aversion to tying the knot again that he is reported to have made a $100,000 bet with Michelle Pfeiffer that he would stay single.

The Lebanese-born Alamuddin, who had no previous connection to Hollywood, has represented Ukrainian former prime minister Yulia Tymoshenko at the European Court of Human Rights, and WikiLeaks founder Julian Assange in extradition proceedings.

"She will keep him on his toes because she is bright," said Judith Graham, 59, from Surrey, England. "He's had all these actresses fawning over him before. I hope he'll be happy".

Alamuddin, who is based in Britain, also advised former United Nations secretary general Kofi Annan on the conflict in Syria, an issue about which Clooney has spoken publicly. Clooney is a strong advocate for human rights, leading several campaigns to bring attention to the plight of refugees in Darfur, Sudan.

The official ceremony is expected to be held on Monday at Venice's town hall, the 14th-century Ca' Farsetti palace, and Italian media reported that the former mayor of Rome, Walter Veltroni, a film buff and Clooney friend, would officiate.

Venice's city government said it would close off a few of the town's narrow pedestrian streets for two hours on Monday.

"Considering that the location of the ceremony is likely to become a target for people attracted by the celebrity status of the event, high numbers could be a problem for traffic and pose a threat to those people's safety," the local government said.