A strong earthquake has struck off the coast of Northern Sumatra, Indonesia. The U.S. Geological Survey has measured the earthquake's magnitude at 8.7, with an aftershock of 6.0 about a half-hour later.

Officials on Indonesia's Nias Island, near the earthquake's epicenter, say dozens of people are trapped in damaged buildings.

The deputy police chief in Gunungsitoli town on Nias Island, told Reuters news service he has seen at least three dead bodies in the wreckage.

The earthquake struck just after 11 P.M. local time (1609 UTC) 200 kilometers west-north-west of Sibolga, Sumatra, Indonesia, about 30 kilometers below the earth's surface.

Officials in Indonesia, Thailand, Sri Lanka and India had issued warnings to their citizens in coastal areas of a possible tsunami.

So far, only a small tsunami has been reported in the remote Cocos Islands more than a thousand kilometers south of Sumatra.

Officials at the Pacific Tsunami Warning Center say authorities can assume the danger has passed if no tsunami waves are observed near the earthquake's epicenter within three hours of the earthquake.

The latest quake is considered an aftershock of the massive earthquake that struck the area December 26, triggering a powerful tsunami that left hundreds of thousands dead or missing in nations bordering the Indian Ocean.