A powerful 7.2-magnitude earthquake struck the Alaska Peninsula region early on Sunday, according to the United States Geological Survey (USGS).

According to initial reports, a tsunami warning was issued after the earthquake.

There were no immediate reports of casualties or damage.

The offshore quake hit at a depth of 21 kilometers off the Alaskan peninsula, the USGS said.

The USGS revised the magnitude of the earthquake down from an initial reading of 7.4.

Tremors were felt across the Alaskan Peninsula, the Aleutian Islands and the Cook Inlet regions, according to the Alaska Earthquake Centre.

The Alaska Volcano Observatory provided a threat notice for the Shishaldin volcano after it sent up a plume of ash earlier Saturday, CNN reported, citing a social media post.

There is a "watch" currently in effect for the Shishaldin volcano, it added.