NEW DELHI, Jan. 14 (Xinhua) -- The Indian government released a five-year plan to reduce the air pollution in the 102 worst-affected cities in the country by 20-30 percent by 2024.

The air pollution level in the Indian capital of New Delhi became severe, officials said on Sunday. The overall air quality index remained in severe category at 414, according to the Indian Central Pollution Control Board.

"We hope this will be a guiding document, a guiding force for all those who join the activities," the Indian Environment Minister Harsh Vardhan told local media.

"These are tough targets, but we believe they are achievable if we do this well," environment secretary Chandra Kishore Mishra said.

The plan outlines multiple actions and their timelines for central ministries, states and city-level agencies seeking to curb vehicular, industrial and thermal power emissions and reduce the air pollution from the burning of crop residue and firewood, brick production, construction and other activities. Some actions are either ongoing or due for immediate implementation, while others have timelines up to 2024.

However, some environmentalists criticized the plan for lacking clear mechanisms or robust funding to achieve its aims. And some observers questioned that the plan may be faced with obstacles as the Indian government focuses on economic growth, with an objective of creating 1 million jobs per month to accommodate India's expanding working class.

Officials asserted that the experiences of cities in other countries suggested that it could take several years for Indian cities to significantly improve their air quality.

Cities "are engines of growth and equity but they have to be sustainable," Amitabh Kant, the chief executive of the Indian central government's think tank, the National Institution for Transforming India, told the New York Times.

India has nine of the world's 10 most polluted cities, according to a World Health Organization measure, with choking urban smog that researchers estimate killed 1.24 million people in 2017.