VENICE, Italy (Reuters) -Global environmental lobby Greenpeace added its voice on Monday to protests against this week's celebrity wedding in Venice between American tech billionaire Jeff Bezos and journalist Laura Sanchez.

The event, expected to attract some 200 guests including U.S. President Donald Trump's daughter Ivanka and son-in-law Jared Kushner, as well as scores of stars from film, fashion and business, has been dubbed "the wedding of the century".

But some locals see the celebration as the latest sign of the brash commodification of a beautiful but fragile city that has long been overrun with tourism while steadily depopulating.

Activists from Greenpeace Italy and UK group "Everyone hates Elon" (Musk) unfolded a giant banner in central St Mark's Square with a picture of Bezos laughing and a sign reading: "If you can rent Venice for your wedding you can pay more tax."

Local police arrived to talk to activists and check their identification documents, before they rolled up their banner.

"The problem is not the wedding, the problem is the system. We think that one big billionaire can't rent a city for his pleasure," Simona Abbate, one of the protesters, told Reuters.

Mayor Luigi Brugnaro and regional governor Luca Zaia have defended the wedding, arguing that it will bring an economic windfall to local businesses, including the motor boats and gondolas that operate its myriad canals.

Zaia said the celebrations were expected to cost 20-30 million euros ($23-$34 million).

Bezos will also make sizable charity donations, including a million euros for Corila, an academic consortium that studies Venice's lagoon ecosystem, Italy's Corriere della Sera newspaper and the ANSA news agency reported on Sunday.

Earlier this month, anti-Bezos banners were hung from St Mark's bell tower and from the famed Rialto bridge, while locals threatened peaceful blockades against the event, saying Venice needed public services and housing, not VIPs and over-tourism.

The exact dates and locations of the glitzy nuptials are being kept confidential, but celebrations are expected to play out over three days, most likely around June 26-28.

($1 = 0.8722 euros)

(Reporting by Ali Kucukgocmen, writing by Alvise Armellini, editing by Gavin Jones and Mark Heinrich)