The earthquake occurred at 1:23 am Pakistani time at a depth of 84 km, the US Geological Survey said.
Its epicentre was 45 km west of Dalbandin, a remote town in Balochistan province with a population of 15,000.
Pakistan Meteorological Department Director Arif Mahmood said the quake was felt in Punjab, Sindh and Balochistan provinces of Pakistan and parts of Iran and India.
He said quakes with such magnitudes in the past had been followed by aftershocks.
Officials said there were apparently no reports of casualties at the epicentre because the region is sparsely populated.
People living near the epicentre in Kalat, Dalbadin and Kharan districts told CNN some mud-walled homes were damaged but no one was hurt.
An official at the Civil Hospital in Balochistan capital Quetta said a female cardiac patient suffered a fatal heart attack during the temblor.
People in Balochistan and Sindh said they had felt buildings sway during the quake.
The temblor shook the cities of Hyderabad, Quetta, Jaffarabad, Lahore and Sargodha.
Residents of high-rise buildings in Karachi rushed out into the streets.
At many places, men and women gathered in open spaces and began praying and reading from the Quran.
Officials in most cities and towns said they had received no reports of casualties or damage.
People in places as far apart as Dubai and New Delhi posted on Twitter that they had felt the quake.
The India Meteorological Department (IMD) said the epicentre of the earthquake was located in southwestern Pakistan in the desert area bordering Iran and Afghanistan.
"It was a shallow earthquake which struck at a depth of 7.4 km," an IMD official said.
The Pacific Tsunami Center said the onshore quake had not triggered a tsunami in the Indian Ocean.
Quakes of 7.0 to 7.9 are classified by geological authorities as major and are capable of causing widespread and heavy damage.
On October 8, 2005, a 7.6-magnitude quake 95 km northeast of Islamabad killed over 70,000 people.