ISLAMABAD, Pakistan (AP) _ A strong earthquake hit northwestern Pakistan and neighboring Afghanistan today, sending Islamabad residents running into the streets of the capital and causing still-undetermined damage in provincial towns.

There were no immediate reports of any casualties. Seismologists in Pakistan put the preliminary magnitude at 6.1 _ the same strength as a Feb. 4 quake that killed an estimated 5,000 people in remote northern Afghanistan.

Today's quake was centered 270 miles northwest of Islamabad in the Hindu Kush range of Afghanistan, according to Sallauddin Khan, director of a Pakistan earthquake center.

The U.S. Geological Survey in Golden, Colo., put the preliminary magnitude at 5.9, but said it may go higher.

The quake was centered 145 miles beneath the earth's surface, far deeper than the quake earlier this month _ an indication damage would likely be less severe.

Khan said there were early reports of damage in northern Pakistani towns of Chitral and Dir. Homes in the region are made of mud and wood, and collapse easily.

In Peshawar, the capital of Pakistan's Northwest Frontier province, people ran from their homes and stood in the street waiting for the tremor to subside, Khan said. The same happened in Islamabad, the national capital.

The epicenter of today's quake was barely 60 miles south of the city of Rustaq, the center of the remote Afghan region hit by the Feb. 4 earthquake.

Aid workers in Rustaq said the tremor was felt there, but it was impossible to immediately the scope of the damage in Afghanistan, if any.

Most people in the area are still living outdoors in makeshift shelters, having lost their homes to the first quake.