There was no other news on the Rialto on Friday as A-list stars glided into Venice to celebrate the wedding of Hollywood hero George Clooney and human rights lawyer Amal Alamuddin.

The two-time Oscar winner and Kentucky-born Clooney, 53, is set to renounce his oath of bachelorhood and marry British-Lebanese barrister Alamuddin, 36, in a multi-day extravaganza in Italy's floating city.

A beaming Clooney and his bride-to-be took a water taxi on the Grand Canal on Friday, and more boats bearing blue flags printed with the initials "A" and "G" waited in the morning at Venice's airport to ferry early arrivals including Ellen Barkin, Clooney's co-star in "Ocean's Thirteen". 

Tourists and Venetians alike clustered after dark on Friday on a pier next to the seven-star Aman Canal Grande Hotel, a fresco-filled palazzo which the pair reportedly reserved for an exchange-of-vows ceremony and reception on Saturday.

Among those hoping to catch a glimpse of one of the glamorous guests on a list rumoured to hold 150 names was Osmany Mena, 37, who was visiting Venice from Miami, Florida.

"They talked about Sandra Bullock, Brad Pitt, Angelina Jolie. It would be cool to see any of them, all of them," Mena said, mentioning Clooney's co-star Bullock in the 2013 blockbuster "Gravity" and another recently married Hollywood power couple.

Local press said Matt Damon, star of "The Talented Mr. Ripley" and "The Bourne Identity", landed later in the day at the airport on Venice's long Lido island.

Alamuddin and Clooney, who vowed never to remarry after his 1993 divorce from actress Talia Balsam, posted legal notice of their plans to wed at a West London town hall in August, drawing a crowd of fans but no appearance from the couple.

Alamuddin has represented Ukrainian former prime minister Yulia Tymoshenko at the European Court of Human Rights, and WikiLeaks founder Julian Assange in extradition proceedings.

She has been dating Clooney since October 2013, according to media reports, and their engagement was confirmed when her legal chambers issued a statement in April to congratulate the couple.

Alamuddin also advised former United Nations secretary general Kofi Annan on the conflict in Syria, an issue about which Clooney has spoken publicly. Clooney also recently worked as an advocate for refugees in Darfur, Sudan.

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Speculation and rumours about the wedding have swirled, but always centred on Italy, where Clooney is a regular attendee of the Venice Film Festival and owns a villa by Lake Como. 

He set off a media frenzy earlier this month when he was widely quoted as saying at an event in Tuscanythat he and his bride-to-be had met in Italy and would marry in Venice.

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, would officiate.

Venice's local 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 notice said. 

Not all Venetians were worried by the prospect of crowds. Marco Pampani, 58, an architect who lives in the city, welcomed the couple's decision to bring their nuptials there.     

"This puts the city in the spotlight," Pampani said by the Aman hotel on Friday evening, still cheery after standing there for 1 1/2 hours. "It brings people, movement, things Venice needs."