Paris has resorted to drastic measures to curb soaring pollution levels by forcing all cars with number plates ending in even numbers off the road for the first time in two decades.

Around 700 police officers were deployed on Monday to man 60 checkpoints around the French capital to ensure that only cars with number plates ending in odd numbers were out on the streets.

The government made the announcement on Saturday after pollution particulates in the air exceeded safe levels for five straight days in Paris and its environs.

Pollution particulates in the air can cause respiratory and heart problems [AFP]

Electric and hybrid cars will be exempted from the ban as well as any vehicle carrying three people or more.

The restrictions came into force across Paris and 22 surrounding areas from 5:30am local Paris time (04:30 GMT) on Monday.

They will be reviewed on a daily basis, with odd numbers potentially banned on Tuesday if an extension is deemed necessary.

Public transport has been free since the weekend to persuade Parisians to leave their cars at home, and the state railway company SNCF warned on its website of packed suburban trains at peak hours due to the extreme measure.

"It is sure we will have more clients today," a delighted taxi driver told the AFP news agency.

Those who choose to brave the ban risk a fine of $30 if paid immediately, or $48 if paid within three days.

'Hasty ban'

It is the first time since 1997 that the French authorities have resorted to such a drastic measure.

Opposition UMP candidate for Paris mayor, Nathalie Kosciusko-Morizet, called the measure a "fig leaf".

Ecology Minister Philippe Martin said he understood the "difficulties, the irritation and even anger" over the move, adding: "But we just had to take this decision."

France's Automobile Club Association (ACA), which counts about 760,000 members, denounced the move as "hasty, ineffective" and "bound to lead to chaos".

"This measure had no effect in any country where it was introduced," said ACA head Didier Bollecker.

"Drivers are being targeted even though heating is more polluting, but no one is asking for heating to be used on alternate days," Bollecker said.

By Saturday the number of pollution particulates in the air had fallen slightly after hitting a high of 180 micrograms per cubic metre - well over double the safe limit - on Friday.

So-called PM10 particulates are created by vehicles, heating and heavy industry, with the safe limit set at 80 per cubic metre.

Pollution particulates in the air can cause asthma attacks as well as respiratory and heart problems. 

Source: AFP