Newlyweds Amazon founder Jeff Bezos and Lauren Sanchez left their luxury hotel on Venice's Grand Canal on Saturday for a final night of partying, crowning a three-day star-studded wedding extravaganza.

Saturday's evening bash -- wrapping up celebrations for 200-250 guests estimated to have cost some US$50 million -- was due to take place in the Arsenale.

Bezos and Sanchez kissed on the boat while greeting those around them.

Around 1,000 people marched against the event on Saturday, groups of activists and residents who object to the wedding and to seeing Venice being gift-wrapped for the uber-wealthy.

Protesters carried banners including one proclaiming 'Kisses yes, Bezos no', playing on Venice's reputation as the city of love.

Venetian businesses and politicians, however, welcomed the event, hailing its major boost for the local economy.

"Those who protest are in contradiction with the history of Venice, which is a history of relations, contacts and business," Mayor Luigi Brugnaro said.

"Bezos embodies the Venetian mentality. He is more Venetian than the protesters."

The city has hosted scores of other VIP weddings, including that of actor George Clooney and human rights lawyer Amal Alamuddin in 2014. (Reuters)