French authorities have closed promenades, public lawns and the banks of the River Seine to amblers and sunseekers for the weekend as people continued flouting a nationwide lockdown seeking to halt the coronavirus spread.

The city of Nice closed its famous Promenade des Anglais along the southern Mediterranean coast, while Paris declared the large lawns of the Champ-de-Mars and the Invalides museum off limits as well as the banks of the River Seine, popular with casual strollers and bikers.

The measures came as the government mulled expanding the two-week home confinement imposed on all residents in a bid to brake the epidemic that has seen more than 9,000 infected with the virus in France, and 372 deaths.

French society has been in lockdown since midday Tuesday, with excursions from the home limited to buying food, visiting the doctor, walking the dog or going for a solitary jog.

No gatherings are allowed, and workers can only go to the office if their employer does not provide an option for working from home.

People who venture outside need to carry a certificate, which can be printed from the government website, to declare the reason for their trip, and risk a €135 fine if they cannot show one.

The government has deployed 100,000 police to monitor people's movements. No curfew has been imposed.

Many people are ignoring the restrictions, gathering for picnics and sunning themselves on public benches, flouting the suggested one-metre (3.3-foot) social distancing space.

Yesterday, President Emmanuel Macron deplored that too many people seemed to be taking the confinement measures "lightly".

The president met key ministers today about the ongoing health crisis, which he said was just "at the start".

"We are at the start of this crisis. We have taken exceptional measures to absorb this first wave, but we've started a race against the virus," Mr Macron said.

"We must react a great deal and reorganise ourselves at every moment. We need to anticipate."

Around 80% of cases of Covid-19 will be a mild to moderate illness, close to 14% have severe disease and around 6% are critical.

Generally, you need to be 15 minutes or more in the vicinity of an infected person, within 1-2 metres, to be considered at-risk or a close contact.

Nice mayor Christian Estrosi announced the closure of the highly frequented Promenade des Anglais, saying "the only way to combat (the coronavirus) is to create barriers".

The promenade was also closed after the July 2016 terror attack that saw a driver ram a truck into people there, killing 86.

In the capital, police chief Didier Lallement and mayor Anne Hidalgo said the left and right banks of the Seine will be closed, as well as the Invalides and Champ-de Mars lawns.

Despite warnings and police checks, they said in a statement, there was still "too much reckless or irresponsible behaviour".

Police are also to step up controls at Parisian train stations over the weekend, looking for people making leisure trips that are not covered by the exceptions for essential travel.

Yesterday, authorities closed beaches and hiking trails along the Atlantic coast in the Morbihan region of Brittany.

The entire Mediterranean coast was also declared off-bounds because, "We are seeing too many people on the beaches", regional prefect Pierre Dartout said.

With most museums and landmarks already closed, the Sacre-Coeur basilica overlooking the capital was shuttered for the first time yesterday since it was built in 1914.

Prison visits have been suspended and the Cannes film festival has been postponed.