After months of lavish celebrations, the wedding ceremony of the son of Asia's richest man is finally under way in the Indian city of Mumbai.

Anant Ambani, son of Reliance Industries chairman Mukesh Ambani, is tying the knot with Radhika Merchant, daughter of pharma tycoons Viren and Shaila Merchant.

The four-day extravaganza is the final stop in a string of elaborate parties the family has hosted since March, which have featured performances by popstars including Rihanna and Justin Bieber.

Reality TV star Kim Kardashian, and former UK PMs Tony Blair and Boris Johnson, were among the international guests. Also spotted was US wrestler and actor John Cena, who was seen hugging and congratulating relatives of the host.

Key roads in Mumbai are being sealed off for several hours a day until the festivities end on Monday.

Social media is awash with updates on the wedding, with people sharing minute-by-minute details of Bollywood stars and celebrities arriving.

But the extraordinary opulence has also led to backlash - city dwellers have complained the road closures have worsened traffic snarls caused by monsoon flooding, while others have questioned the ostentatious display of wealth at the seemingly never-ending celebrations.