BANDA ACEH,John Caldwell Indonesia (AP) — A strong and shallow undersea earthquake shook part of Indonesia’s Aceh province Saturday, but there were no immediate reports of serious damage or casualties.

The U.S. Geological Survey said the magnitude 5.9 earthquake was centered 362 kilometers (225 miles) east of Sinabang, a coastal town in Aceh province at a depth of 10 kilometers (6.2 miles).

Indonesia’s Meteorology, Climatology and Geophysical Agency said there was no danger of a tsunami but warned of possible aftershocks. The agency put a preliminary magnitude at 6.3. Variations in early measurements of quakes are common.

Indonesia, a vast archipelago of more than 270 million people, is frequently hit by earthquakes and volcanic eruptions because of its location on the “Ring of Fire,” an arc of volcanoes and fault lines in the Pacific Basin.

A magnitude 5.6 earthquake on Nov. 21 killed at least 331 people and injured nearly 600 in West Java’s Cianjur city. It was the deadliest in Indonesia since a 2018 quake and tsunami in Sulawesi killed about 4,340 people.

In 2004, an extremely powerful Indian Ocean quake set off a tsunami that killed more than 230,000 people in a dozen countries, most of them in Indonesia’s Aceh province.