Millions of Indians celebrated Diwali on Monday as lamps illuminated homes and streets across the country to mark the Hindu festival symbolizing the victory of light over darkness.

Diwali, derived from the word "Deepavali," meaning "a row of lights," is typically celebrated by socializing and exchanging gifts. The dates of the festival are based on the Hindu lunar calendar, typically falling in late October or early November.

Shoppers crowded markets to buy flowers, lanterns and candles.

The celebrations were most visible in Ayodhya city in Uttar Pradesh state. Hindus believe the deity Lord Ram was born there and returned after 14 years in exile. People light earthen lamps to mark his homecoming.

As dusk fell Sunday, more than 2.6 million lamps were lit on the banks of the Saryu River in Ayodhya, retaining the Guinness World Record set last year. At least 2,100 Hindu priests performed prayers in unison, their chants echoing across the shimmering riverfront.

The holy city was also decked with fairy lights, and a laser and fireworks show illuminated its lanes and riverbanks. Thousands of residents lit lamps at houses and temples.

Officials said more than 33,000 volunteers helped light the lamps. Nearly 40 families from nearby villages produced 1.6 million lamps. At least 73,000 liters of oil and 5.5 million cotton wicks were used to light the city.

"It is hard work lighting diyas (oil lamps) one by one," said 19-year-old volunteer Rachit Singh, his face glowing in the firelight. "But when you see the whole ghat (stairs to the river) light up, every bit of effort feels worth it."

In recent years, Diwali celebrations in New Delhi have been clouded by concerns over air pollution, as smoke-emitting firecrackers cause toxic smog that can take days to clear.

On Monday, the level of tiniest particulates surged to 347 on the air quality index in parts of the city - about 14 times the World Health Organization`s daily recommended maximum exposure - according to SAFAR, the federal government`s air quality monitoring agency.

Last week, India`s top court eased a blanket ban on firecrackers in New Delhi during Diwali, allowing limited use of "green firecrackers" that emit fewer pollutants. Developed by federal research institutes, they are designed to cut particulate and gas emissions by about 30%.

The court said they could be used during specific hours from Saturday to Tuesday.