A powerful earthquake jolted Pakistan shortly before dawn Friday, sending panic-stricken city residents running into the streets. The official news agency said up to 75 people were killed and 100 injured.

In the dusty northwest frontier province, at least 100 sun-baked mud houses shook and crumbled, crushing to death people sleeping inside, the reports said. Most of the reported dead lived in that area, about 400 miles from the epicenter in neighboring Afghanistan.The quake, whose epicenter was in central Afghanistan about 200 miles northeast of Kabul, registered 6.8 on the Richter scale, the Associated Press of Pakistan reported.

There were no immediate reports of casualties in Afghanistan, but there are no communication links with the neighboring country.

The jolt rattled windows in the capital of Islamabad. Frightened residents ran from their homes.

The hardest hit people in the northwestern province were Afghan refugees living in squalid camps. More than 3 million Afghans fled to Pakistan after 1979, when the Soviet Union sent troops to fight in the civil war there.

"(The quake) was very deep, so it probably was felt throughout the area, but I wouldn't expect much damage," said Russ Needham, a geophysicist with the U.S. National Earthquake Information Center in Golden, Colo. "That's a fairly sparsely populated area."

However, about 2 million people live in Kabul.

The Soviet Union's official news agency, Tass, said the quake was also felt in the central Asian republics of Uzbekistan and Tadjikistan. But no casualties were reported there.