The US Geological Survey said the 6.8 magnitude quake was 57 km (35 miles) deep and struck 29 km (18 miles) west of Imphal, capital of India's Manipur state, which borders Myanmar.
The pre-dawn quake killed six people in India and five in neighboring Bangladesh, officials said, while shockwaves were felt in the Himalayan nation of Nepal and as far away as the Myanmar city of Yangon, about 1,175 km (730 miles) to the south.
The quake struck while many people were asleep, and roofs and staircases of some buildings collapsed in Imphal, a city of about 270,000 people.
"It was like being tossed around in a frying pan," said Joy Thanglian, a 33-year-old employee of state energy firm Bharat Petroleum.
Police and hospitals in Imphal said the death toll had reached six with 100 people injured, 33 of them seriously.
Officials in Bangladesh said as well as the five people who died of heart attacks as they fled buildings, about 90 people were injured.
Rescue workers in Imphal used hand-held drilling machines to clear rubble from the ruins of a six-storey building under construction, the site of the heaviest damage in the city.
"I didn't feel the tremor, but when I woke up the entire ceiling had collapsed on me," said R.K. Ewansana, a 21-year-old student, who was on the first floor but survived as the rest of the building collapsed around him.
Residents said people fled from their homes, and power and telecoms links were down in the remote region.
At Imphal's airport, flights were normal, although a boundary wall collapsed, and a crack appeared in the terminal building, said Thanglian, who works there.
Some people criticised what they called the authorities' slow response, saying that although the army had begun to clear debris, it appeared to be short of heavy equipment.
"We haven't seen any help from the government side," said disaster volunteer worker Kangujam. "The government has not given us any information."
The government said two teams from the National Disaster Response Force had arrived to help with the rescue.
"The rescue operations are about to start on a war footing," Junior Home Affairs Minister Kiren Rijiju told Reuters.
Indian Prime Minister Narendra Modi tweeted that he was in touch with authorities in the northeast.
Manipur is one of seven northeastern provinces joined to the rest of the India by a thin strip of territory arching above Bangladesh.
It was the most powerful earthquake to hit the state since 1957, according to academics at the department of seismological research at Manipur University. — Reuters
