Residents of the city of Adak on Alaska's Aleutian Islands evacuated the town site and gathered on a nearby hill Monday after a magnitude-8.0 earthquake prompted a tsunami warning for part of the island chain.

"We're seeing water leave our bay, so we do have everybody up on the Bering Hill area, where our primary evacuation center is at," City Manager Layton Lockett told The Associated Press by telephone as he gathered some last paperwork before heading out himself to join about 300 residents at the center.

About 200 miles west, a tsunami wave of about 7 inches was reported at Amchitka Island, said Jeremy Zidek, a spokesman for the Alaska Department of Homeland Security and Emergency Management.

There were no immediate reports of damage, he said, as authorities with the state emergency system began notifying the coastal communities affected by the tsunami warning or the tsunami advisory that was issued for coastlines further from the earthquake's epicenter.

Natasha Ruppert, a seismologist with the Alaska Earthquake Center, said that because the communities that would have suffered damage are under a tsunami warning, people may not have been able to get out and check for damage yet.

The earthquake was widely felt in Adak, one of the largest cities in the affected area about 1,300 miles southwest of Anchorage. Shaking could also be felt in Shemya and other villages along the sparsely populated Aleutian Islands.

Shemya Island is where the U.S. military operates Eareckson Air Station, which serves mainly as an early warning radar installation.

The earthquake recorded at 12:53 pm Alaska Daylight Time was initially reported with a magnitude of 7.1, but that was upgraded to 8.0, Ruppert said. The quake was centered about 13 miles southeast of Little Sitkin Island or 25 miles north Amchitka Island.

Amchitka is where the government tested nuclear weapons underground in the 1960s and 70s. The tests included one of the United States' largest nuclear explosions ever.

The quake was recorded at a depth of 60 miles, which is relatively shallow for an earthquake in the Aleutian Islands. The shallower the quake, the more likely it will be felt.

The quake was followed 18 minutes later by a magnitude-6.0 aftershock, and at least three more aftershocks followed with magnitudes ranging from 4.8 to 5.9.

The National Tsunami Warning Center in Palmer, Alaska, issued a tsunami warning for coastal areas from Nikolski, population 18, and Attu, which is near the tip of the Aleutians. A warning means significant inundation is possible or occurring. Residents were being warned to move inland toward higher ground.

A tsunami advisory was also issued for coastal areas between Nikolski and Unimak Pass, which is further east. That area includes Unalaska, a city of about 4,000 people. An advisory means strong currents or dangerous waves are expected, but widespread inundation isn't likely.