Cannes is never out of the spotlight.

As the curtain rises on the G20 summit, it is not only world leaders who are ready to be featured in close-up shots in southern France's movie mecca; so are policemen and protesters.

The leaders of 20 countries whose economies make up 85 percent of the world economy have arrived at the coastal town for a two-day discussion about some of the most pressing issues in the world today, such as the eurozone's debt crisis and banking regulations.

The town's most common sights now include banners reading "New World, New Ideas" - the summit's slogan of the summit - and police officers.

Media have recently reported that about 12,000 police officers from throughout France have been sent to the Cote d'Azur resort town.

Several of the policemen who were among those transferred temporarily to Cannes from other French cities confirmed the accuracy of that number, saying they are not allowed to give their names for attribution.

Cannes' famous Croisette seafront, the site of the summit's main venue, Le Palais des Festivals, is open only to those who hold a security pass. The surrounding area will be guarded around the clock on Thursday and Friday.

A week ago, residents began finding police notices warning about possible disruptions. Many shops, especially those within the Croisette area, are closed.

"Some worry about protests or violence," said an eyeglass shop owner who would only give his first name, Sebastian. "Others find tourists are less because of the seafront is cordoned."

"We feel safe when many policemen are nearby, but it will be easier for our life when the summit finishes," he said.

Pointing outside his shop, he said he hears "sirens all day".

He said he is not as worried about the event as are his fellow shop owners who have closed their businesses, but is "ready to shut when violence happens".

In Nice, also in France, thousands of protesters marched on Tuesday and Wednesday.

A group of NGOs, including Oxfam - which fights poverty and injustice - and Action against Hunger, have taken up the slogan "People First, Not Finance" and are calling on world leaders to pay more attention to the poorest instead of the richest.

"Legitimate, peaceful protest is a vital part of persuading governments that there is massive public concern about the levels of poverty and suffering in today's world - and that governments and global institutions are not doing enough to tackle it," said Magali Rubino, a press officer with Oxfam.

The coalition of protesters expects to rally 10,000 people for an "alternate summit" in the next two days.

Police in Nice arrested three Spanish men on Tuesday who were suspected of possessing "bolts, mountaineering axes, balaclavas and gas masks".

The summit this year is almost certain to come under special attention as it comes at a time when the world economy is at risk of falling into recession. Yet, despite what would seem to many to be an obvious need for action, there is always the danger that the event will produce few results of importance, experts warned.

"G20 countries may agree on some further strategic directions, and it would be helpful if they could show the sort of determination to confront global problems that it did in 2008-09, but has lost since," said Iain Begg, professor of the London School of Economics and Political Science.