People attend the Dinner In White event in front of the Notre Dame Cathedral in Paris. Participants who attend the dinner, which takes place at a different place in Paris every year, are required to be dressed in white and bring their own food, drink and cutlery.

Paris - Leave it to the Parisians to organise the most sophisticated - and gastronomic - flash mobs.

Thousands of locals gathered in the city's Place des Vosges on Thursday night for an impromptu open-air dinner, dressed head to toe in white and bringing with them white tablecloths, glassware and other finery.

Participants at the “Diner En Blanc” (Dinner In White) were told of the venue via social media sites and the Internet, then rushed to assemble in the heart of Paris' Marais district, in a 25-year-old tradition that still leaves passersby open-mouthed.

Last year, thousands gathered in front of Notre Dame cathedral at twilight for what organisers call a “chic picnic in a public space”, waving their white napkins at the appointed time before digging in to enjoy their meals.

Other venues in Paris have included the Eiffel Tower, the Louvre Museum's courtyard, Les Invalides, the final resting place of Napoleon, and the famed Champs-Elysees.

“It's a sort of ritual, a need for social contact. It's a chance to get together and meet new people,” said Claire Verckel, a regular at the gourmet event.

Sheltered by the cloistered arcades of Paris's oldest square, diners raised glasses in toasts and savoured their meals by candlelight, while in the background a white grand piano provided musical accompaniment.

“I came out of curiosity, but the atmosphere is amazing,” said first-timer Arnaud Bonichon.

The pop-up event is so popular it has been picked up around the world, with Diner En Blanc events planned this year for the United States, Canada, Spain, Singapore, Mexico and even Rwanda.

In earlier years, the event was strictly word-of-mouth, but as it has grown, new rules have taken shape. Today, one must be invited by a participant from the previous year or be on the website's waiting list.

Guests must bring a table and two white chairs, a picnic basket filled with “quality menu items” and a dinner service, including stemware and flatware.

Only wine or champagne are allowed, as beer and hard alcohol drinks are considered no-nos.

The goal of the event is simple, organisers say: “To gather at a secret location with the sole purpose of sharing a high-quality meal with good friends at the heart of one of the city's most beautiful locations.” - Reuters