A Delhi court on Monday rejected a legal challenge to driving restrictions aimed at reducing pollution in the smog-choked Indian capital.

The court said the Delhi government could continue to ban most private cars from the city's roads on alternate days until Friday, when a 15-day trial of the scheme is due to end.

The restrictions are part of a slew of initiatives announced last year by the Delhi government, under pressure to improve air quality in the world's most polluted capital.

A number of challengers had argued that they were not effective in bringing down pollution, and that the city's public transport system was not up to the task.

"All the petitions challenging the odd-even policy have been dismissed. We will continue with the scheme," the government's lawyer Rahul Mehra told AFP.

However, the court said the Delhi government should consider such concerns before implementing permanent restrictions.

Authorities have already said the scheme may be extended beyond Friday if it is successful.

Environmentalists have welcomed the restrictions, but say they are unlikely to make a dramatic difference in the short term.

The US embassy in Delhi put PM2.5 levels at 97 on Monday afternoon -- lower than earlier in the day, but still nearly four times World Health Organization safe limit of 25.

PM2.5 refers to microscopic particles that penetrate deep into the lungs and are particularly harmful to health.

Delhi's air quality traditionally worsens in winter as the cooler air traps pollutants and people start lighting fires.

A 2014 WHO survey of more than 1,600 cities ranked Delhi as the most polluted, partly because of the 8.5 million vehicles on its roads.