A vehicle rationing scheme has been introduced by the Indian capital, Delhi, as it fights alarming levels of pollution.

Only cars with either odd or even number plates will be permitted on the roads every day from 4 to 15 November, officials said.

Such a system was previously used, but it is not clear whether it actually helps to reduce pollution.

Hazardous particle rates in the atmosphere-known as PM2.5-are well above 10 times safe limits.

Cars are not thought to be the main cause of Delhi's toxic air, however, with experts pointing to farmers in neighboring states burning crops to clear fields instead.

Health officials have asked people to stay indoors and refrain from doing any physical activity as millions are at risk of respiratory illness. Schools are closed until Tuesday and the shutdown is likely to be extended until Friday as the city continues to choke under a thick blanket of smog.

Delhi Chief Minister Arvind Kejriwal said the car rationing system, known as the "odd-even plan", would take hundreds of thousands of cars off the road. Those ignoring the rule will be fined 4,000 rupees ($56) - double that of previous years.

Only public transport, emergency vehicles, taxis and two-wheelers will be allowed. Women driving alone will also be exempt from the rule.