A powerful earthquake struck South Asia before dawn on Monday, killing at least nine people and injuring nearly 200, with efforts to rescue those trapped in rubble hampered by severed power supplies and telecommunication links.

The U.S. Geological Survey said the quake of magnitude 6.8 was 57 km (35 miles) deep and struck 29 km (18 miles) west of Imphal, the capital of Manipur, bordering Myanmar.

The quake struck while many residents were asleep, and roofs and staircases of some buildings collapsed in the 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. "Then we ran outside."

Police and hospitals in Imphal said the toll had reached six dead, with 100 people injured, 33 of them seriously.

"It was the biggest earthquake we've felt in Imphal," disaster response worker Kanarjit Kangujam told Reuters by telephone.

Rescue workers battled to find workers believed to have been buried beneath the rubble of a building that had been construction. They were unsure how many might be trapped.

Residents of Imphal said people fled their homes and power and telecoms links were down in the remote region.

At the 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."

Government officials leading the rescue effort could not immediately be reached for comment.

Indian Prime Minister Narendra Modi tweeted that he was in touch with authorities in the northeast. Rescue teams from Guwahati, in neighbouring Assam state, were scrambling to reach Imphal.

People in Bangladesh and the Himalayan nation of Nepal ran from their homes, and the quake was also felt as far away as the Myanmar city of Yangon, about 1,176 km (730 miles) to the south, residents said.

Media in Bangladesh reported three people died of heart attacks with police saying at least 90 were injured.

An official at Myanmar's meteorological department in Naypyitaw, the capital, said there were no reports of damage or casualties on the Myanmar side of the border.

READ: Quake strikes northeast India; toll reaches four dead, nearly 100 injured