Air pollution level in Delhi has dropped to 'hazardous' level on Sunday with an overall Air Quality Index (AQI) of 625 - the highest this year - at around 10 am.

The air quality of Delhi and regions around it remained toxic between "severe" and "very-poor" levels even five days after Diwali, with weather conditions expected to be unfavourable till at least November 15.

In a major measure which can curb pollution coming to Delhi from adjoining states, the central government is likely to impose an obligation on thermal power plants to mix coal with a 10 per cent component of straw pellets or briquettes, the Union Power Minister R.K. Singh said on Thursday.

It was a misty Thursday morning in the national capital with the minimum temperature recorded at 13 degrees Celsius, which is the season's average.

National Green Tribunal on Monday rebuked the Delhi Government for not filing the review petition of its order against an exemption to women drivers, two-wheelers and government servants in the proposed Odd-Even rule to tame pollution.

With Delhi's air quality severe since the last four days, the NGT on Friday rapped the governments of Delhi and neighbouring states, saying "you've earned Delhi the title of the worst capital in the world" and ordered them to ensure an end to stubble burning.

The country's top green court on Friday questioned the efficacy of the Delhi government's proposed odd-even vehicle rationing scheme that was to be rolled out from Monday as the capital and its suburbs remained shrouded in a dense haze, with air pollution levels continuing to be "severe".

Delhi education minister Manish Sisodia on Tuesday ordered primary schools to remain closed until further notice in view of the dense smog covering the national capital.

With the air quality in Delhi and NCR getting worse ahead of winter, the city government has said it may bring back the odd-even vehicle rationing scheme in the capital.

Prayer for Peace is a landmark event in the spiritual calendar of Delhi that intends to transform the city by bringing together diverse spiritual and religious leaders and their followers for a Group Meditation for World Peace.