The death toll could climb because communications were down in much of the rugged Hindu Kush mountain range area where the quake was centred.

In one of the worst single incidents, a panicked evacuation at girls' school killed at least 12 students in the Afghan province of Takhar.

"They fell under the feet of other students," said Abdul Razaq Zinda, provincial head of the Afghan National Disaster Management Agency, who reported heavy damage in Takhar.

Shockwaves were felt in northern India and in Pakistan, where hundreds of people ran out of buildings as the ground rolled beneath them.

"We were very scared ... We saw people leaving buildings, and we were remembering our God," Pakistani journalist Zubair Khan said by telephone from the Swat Valley north-west of the capital, Islamabad.

"I was in my car, and when I stopped my car, the car itself was shaking as if someone was pushing it back and forth."

The US Geological Survey initially measured the quake's intensity at 7.7 then revised it down to 7.5.

In Afghanistan, where rescue and relief work is likely to be complicated by security threats created by an escalating Taliban insurgency, at least 52 people were reported dead in several provinces.

In Pakistan, the head of the Khyber Pakhtunkhwa Provincial Disaster Management Agency, Amer Afaq, said the death toll had reached 167, while military spokesman General Asim Bajwa said nearly 1000 were injured.

The quake was 213 kilometres (132 miles) deep and centred 254 kilometres (158 miles) north-east of Kabul in Afghanistan's Badakhshan province.

Dr John Ebel, chairman of the Department of Earth and Environmental Sciences at Boston College in the United States, said the depth of the earthquake meant damage was likely to be spread broadly rather than focused in one disaster zone.

But he said landslides on the unstable slopes of the mountainous region could pose a major problem to rescuers in the coming days.

"Obviously if a landslide comes in to a village, it will take out buildings, but landslides can also take out roads and communications and power systems, so you lose the ability to access remote areas," he said.

Buildings in the Pakistani capital, Islamabad, shook for several minutes when the quake hit just before 3pm local time.

EXCLUSIVE VIDEO: People in Noida rush out of offices as #earthquake tremors rocked the capital pic.twitter.com/tn6py68MMM— SkymetWeather (@SkymetWeather) October 26, 2015

In the Pakistani city of Peshawar, the Lady Reading Hospital has been inundated with people injured as buildings crumbled.

"We received 50 injured and more are being shifted. The injured suffered multiple injuries due to building collapse," hospital spokesman Syed Jamil Shah told Reuters.

Hundreds of people raced from buildings onto the streets in New Delhi while the quake was also felt in the Himalayan region of Kashmir, according to an AFP reporter.

Power outages have affected communication lines in Kabul as well, according to local news reports

Some Kabul mobile networks down and power outages reported after powerful earthquake jolts Afghanistan, India and Pakistan— TOLOnews (@TOLOnews) October 26, 2015

In Pakistan, the northern area of Chitral, where 20 people were killed, was particularly hard hit.

"We are not able to contact people in remote areas due to telephone lines being down, so there are chances that the death toll could rise," Jehan said.

Further south, the city of Peshawar reported two deaths and at least 150 injured people were being treated at the city's main hospital, the provincial health chief said.

In Afghanistan, international aid agencies working in northern areas reported that mobile phone coverage in the affected areas remained down in the hours after the initial quake.

"The problem is we just don't know. A lot of the phone lines are still down," said Scott Anderson, deputy head of office for the U.N. Office for the Coordination of Humanitarian Affairs (OCHA) in Kabul.

Badakhshan provincial governor Shah Waliullah Adib said about 400 houses were destroyed but he had no figures on casualties.

"Right now we are collecting information," he said.

Aftershocks are likely in next 24 hours, according to Pakistan's National Disaster Management Authority.

Pakistani Army troops were ordered to provide relief to any people affected by the quake, and Prime Minister Nawaz Sharif asked rescue workers to be on alert, the New York Times reported.

Indian prime minister Narendra Modi said his government was ready to provide assistance to Kabul and Islamabad.

"Heard about strong earthquake in Afghanistan-Pakistan region whose tremors have been felt in parts of India. I pray for everyone's safety," Mr Modi said on Twitter.

"I have asked for an urgent assessment, and we stand ready for assistance where required, including Afghanistan and Pakistan," he said.

Heard about strong earthquake in Afghanistan-Pakistan region whose tremors have been felt in parts of India. I pray for everyone's safety.— Narendra Modi (@narendramodi) October 26, 2015

The earthquake struck almost exactly six months after Nepal suffered its worst quake on record, on April 25. Including the toll from a major aftershock in May, 9,000 people lost their lives and 900,000 homes were damaged or destroyed.

The mountainous region is seismically active, with earthquakes the result of the Indian subcontinent driving into and under the Eurasian landmass. Sudden tectonic shifts can cause enormous and destructive releases of energy.

A 7.6 magnitude earthquake struck northern Pakistan just over a decade ago, on Oct. 8, 2005, killing about 75,000 people.

Reuters

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