The police admitted there were violations, and that they would take serious legal action against firecracker sellers.

The police said it seized over 1,300 kg of firecrackers during the overnight operation on Diwali across the national capital, arrested over 300 people and registered more than 600 FIRs.

The Supreme Court had allowed bursting of firecrackers from 8 pm to 10 pm on Diwali. It had also allowed manufacturing and sale of only "green crackers", which have a low light and sound emission and contain less harmful chemicals.

The court had asked the police to ensure that banned firecrackers were not sold and said in case of any violation, the station house officer (SHO) of the police station concerned would be held personally liable. Any violation would amount to committing contempt of court, the apex court had warned.

"The Air Quality Index (AQI) of Delhi and the National Capital Region between 8 and 9 p.m. on Wednesday was recorded around 150-160. It continued to rise and crossed 250 (severe category) by 3 a.m. It crossed 300 (very severe category) by 6 a.m.," an official of the Centre for Science and Environment (CSE) told IANS.

"The AQI index increased because of firecrackers," said the official.

The official said the CSE has not taken a firm stand on firecrackers this time. "But we can says the pollution level was 6.5 times higher in Delhi and NCR than the standard (60) category from Diwali night to Thursday morning," said the official.

Delhiites continued to burst firecrackers on Diwali long after the 10 p.m. deadline. Despite stringent rules, the people managed to buy firecrackers illegally from the sellers in neighbourhood markets.

Violations of the Supreme Court order were reported from IP Extension, Mayur Vihar's Phase-I, II and Extension in east Delhi, Lajpat Nagar in south Delhi, Lutyens Delhi, Dwarka in west Delhi and most of the sectors in Noida.

"We received 1,400 PCR (Police Control Room) calls between Wednesday evening and Thursday morning about firecracker bursting. By and large the people did not violate the Supreme Court rules, but there were some incidents. As our police personnel were patrolling the whole night, we booked the violators," Delhi Police spokesperson Madhur Verma said.

Over 700 kg of firecrackers were seized from south Delhi, 140 kg from North West Delhi, 200 kg from Dwarka, 278 kg from South East and 72 kg form North Delhi, police said.

The Delhi Fire Service (DFS) department said it received 501 calls within 32 hours -- between midnight on Wednesday and 8 a.m. on Thursday. The number of calls was the highest since 2007, the DFS said.

The number of calls received by DFS during Diwali was 204 in 2017 and 243 in 2016, 290 in 2015, 211 in 2014, 177 in 2013, 184 in 2012, 206 in 2011, 169 in 2010, 207 in 2009, 158 in 2008 and 184 in 2007.

Chief fire officer Atul Garg told IANS the fire-related calls were received from across the national capital and the peak time was from 6 p.m. on Wednesday to 6 a.m. on Thursday. "A total of 223 calls were received during this period," he said.