A strong earthquake and nerve jangling aftershocks cracked walls and sent inhabitants pouring onto the streets in several towns across northeastern India on Wednesday.

There have been no reports of casualties so far, with residents saying the main human toll was stress, minor cuts and bruises.  

The US Geological Survey said the epicentre of the 6.0 magnitude quake was in a hilly region in Assam state near India's border with Bhutan. 

Both the main tremor and aftershocks were felt hundreds of kilometres away in the northern state of Bengal, as well as in Bhutan and Bangladesh.

The quake badly shook Tezpur, a city of 100,000 people, about 45 kilometres (28 miles) from the epicentre.

"It lasted more than 20 seconds and we were really scared," Tezpur resident Swati Deb Dey told AFP.

"The walls shook as we ran downstairs and even outside the road was moving. Everyone is shocked," she added.

Residents said many buildings suffered cracked walls and broken windows. Fissures spread across roads.

"There are some cracks in pillars and walls but no major damage or casualties so far," said Mugdhajyoti Dev Mahanta, a police superintendent for Sonitpur district, which includes Tezpur.

"Our teams are on the ground and assessing the situation."

Aftershocks spread

In Assam's main city, Guwahati, about 150 kilometres (95 miles) to the south, the quake shook buildings and chunks of concrete fell off the side of buildings that were cracked.

Residents said at least two big aftershocks were felt.

In Nagaon, one apartment block tilted onto an adjacent building.

Assam's Health Minister Himanta Biswa Sarma tweeted photos of broken walls in a Guwahati building minutes after the quake.

India's Prime Minister Narendra Modi said he had spoken with state authorities and promised assistance from the central government. 

"I pray for the well-being of the people of Assam," Modi said on Twitter.

According to the USGS, the quake's relatively shallow depth of 34 kilometres (21 miles) had increased the risk of severe damage.

It said the main tremor struck at 0221 GMT in hills just north of Dhekiajuli, a town in a tea-growing district of northern Assam.

A second one with a magnitude of 4.0 hit 10 minutes later and others followed.

The Himalayan region is notorious for big earthquakes that hit each year.

A 1950 quake killed about 4,800 people in Assam and Tibet. 

The Great Assam Earthquake of 1897 is said to be one of the most powerful to have hit India, leaving hundreds dead in the remote hills.