The Pakistani military said it was rushing troops and helicopters to Baluchistan province's Awaran district, where the quake was centered, as well as the nearby area of Khuzdar.
Most people were killed when their houses collapsed before they could rush outside occurred when houses collapsed on people inside, according to the chief spokesman for the country's National Disaster Management Authority, Mirza Kamran Zia, who gave the casualty toll. He warned that the death toll might rise and said they were still trying to get information from officials in the district.
"We all ran out for safety in the open field in front of our house. Many other neighbors were also there. Thank God no one was hurt in our area but the walls of four or five house collapsed," said Khair Mohammed Baluch, who lives in the town of Awaran, roughly 50 kilometers (30 miles) south of the epicenter.
Pakistan's chief meteorologist, Mohammed Riaz, put the magnitude of the quake at 7.7, while the U.S. Geological Survey in Golden, Colo. Said it was magnitude 7.8.
Baluchistan is Pakistan's largest province but also the least populated. The head of Pakistan's Earthquake Center, Zahid Rafi, warned of possible aftershocks.
The area where the quake struck is at the center of an insurgency that Baluch separatists have been waging against the Pakistani government for years. The separatists regularly attack Pakistani troops trying to suppress the uprising as well as symbols of the Pakistani state, such as infrastructure projects.
Baluchistan is also poorly developed with little economic development.
The quake was felt as far away as New Delhi, the Indian capital, but no damage or casualties were immediately reported there, said Jai Chandra, a meteorologist with the India Meteorological Department.
The quake also jolted Pakistan's largest city, Karachi, along the Arabian Sea, roughly 250 kilometers (155 miles) from the epicenter. People in the city's tall office buildings rushed into the streets following the tremor, and Pakistani television showed images of lights swaying as the earth moved.
"I was working on my computer in the office. Suddenly I felt tremors. My table and computer started shaking. I thought I was feeling dizziness but soon realized they were tremors," one Karachi resident, Mohammad Taimur, said.
A security guard at a bank in one of the buildings said he locked the doors after everyone left the office, then rushed into the street.
"At the time I felt the strong shock, I went inside the office to watch the TV. Other people were yelling 'Earthquake! Leave the office!" said Muhammad Akhtar.
In Quetta, the capital of Baluchistan, people also fled their homes and offices in panic.
Matiullah Khan, a cellphone vendor in Quetta, said he was in his shop with a customer when the cabinet and shelves started to shake.
"I along with customers rushed out to the main street ... Thousands of people were standing, many in fear and reciting Quranic verses," he said, referring to Islam's holy book.
Baluchistan and neighboring Iran are prone to earthquakes.
A magnitude 7.8, which was centered just across the border in Iran, killed at least 35 people in Pakistan last April.
In January 2011, a 7.2 magnitude quake damaged 200 mud-brick homes in a remote area of Baluchistan about 200 miles (320 kilometers) southwest of Quetta not far from the Afghan border, but caused no casualties.
Ahmed reported from Islamabad. Associated Press writers Asif Shahzad and Zarar Khan in Islamabad, Adil Jawad in Karachi and Ashok Sharma in New Delhi contributed to this report.