The moon passes between the sun and the earth during a total solar eclipse Wednesday over the northern Indian city of Varanasi. (Jayanta Shaw/Reuters)

The longest solar eclipse of the 21st century pitched a swath of Asia into near-darkness after dawn Wednesday, as millions watched the once-in-a-lifetime phenomenon.

Live television pictures showed the sun completely blotted by the moon in Taregna, a village in eastern India, at 6.24 a.m. local time (8:54 p.m. ET Tuesday).

Students try solar eclipse goggles after a demonstration on how to safely watch a solar eclipse in Allahabad, India, on Tuesday. (Rajesh Kumar Singh/Associated Press)

But most other parts of India remained under thick cloud cover, to the disappointment of millions who gathered outside to watch the event.

The eclipse lasted six minutes and 39 seconds at its maximum point. It was later seen in a broad swath moving north and east to Nepal, Myanmar, Bangladesh, Bhutan and China. It was visible only in Asia and was the longest total eclipse since July 11, 1991, when one lasting six minutes, 53 seconds was visible from Hawaii to South America.

There will not be a longer eclipse than Wednesday's until 2132.

One of the best views appeared to be in the Indian town of Varanasi, on the banks of the Ganges River, sacred to devout Hindus. Thousands of Hindus took a dip in keeping with the ancient belief that bathing in the Ganges at Varanasi, especially on special occasions, cleanses one's sins. The eclipse was seen there for three minutes and 48 seconds.

But the gathering was marred by tragedy when a 65-year-old woman was killed and six people were injured in a stampede where about 2,500 people had gathered on the riverbank, said police spokesman Surendra Srivastava. He said it is not clear how the stampede started.

Over the past week, Taregna had been overrun by researchers who planned to study scientific phenomena ranging from the behaviour of birds and other animals to atmospheric changes affected by the eclipse.

Hotels in Patna were fully booked while taxis raised their rates, sensing a brief opportunity in the sudden interest in the village.

Clouds, rain frustrate scientists

A 10-member team of scientists from the Indian Institute of Astrophysics in Bangalore and the Indian air force filmed the eclipse from an aircraft.

But the thick clouds and overnight rains meant thousands of scientists, students and nature enthusiasts on the ground saw just a cloudy darkness.

Although the scientists were disappointed, the rain was welcomed by many in the agricultural area, which has seen scant rainfall this monsoon season. "It would have been nice to see the solar eclipse, but the rain is far more important for us," farmer Ram Naresh Yadav said.

Millions across India shunned the sight and stayed indoors.

Even in regions where the eclipse was not visible, pregnant women were advised to stay behind curtains. Superstition says that the sun's invisible rays could harm a fetus and the baby would be born with disfigurations, birthmarks or birth defects.

"My mother and aunts have called and told me stay in a darkened room with the curtains closed, lie in bed and chant prayers," said Krati Jain, 24, a software professional in New Delhi who is expecting her first child.

Thai monks pray for good luck

In the northern Indian state of Punjab, authorities ordered schools to begin an hour late to prevent children from venturing out and gazing at the sun.

At a Buddhist temple in the Thai capital Bangkok, dozens of monks led a mass prayer at a Buddhist temple to ward off what they said would be ill effects from the eclipse.

"The eclipse is bad omen for the country," said Pinyo Pongjaroen, a prominent Thai astrologer. "We are praying to boost the fortune of the country."

Still, it was not all gloom and doom. A travel agency in India ran a charter flight to watch the eclipse by air, with seats facing the sun selling at a premium.

Back on the ground, additional police and paramilitary troops were posted around Patna and Taregna after Maoist rebels called for a strike Wednesday to protest against the rise in the price of gas and other essential commodities.