Air quality in India’s capital Delhi has deteriorated to severe and extremely poor levels in the past few days, data shows.

Pollution levels crossed 25-30 times the World Health Organization (WHO)’s recommended safe limit at several locations in the city last week.

Experts have warned that the situation will worsen in the coming days due to weather conditions, use of firecrackers during the festival of Diwali on Thursday and burning of crop remains in neighbouring states.

Delhi and several northern Indian cities report extreme levels of air pollution between October and January every year, causing disruption to businesses, shutting down of schools and offices.