JAKARTA, INDONESIA -- A strong undersea earthquake shook Indonesia's northernmost province of Aceh on Saturday, but there were no immediate reports of serious damage or casualties and officials said there was no threat of a tsunami.

Witnesses said many people ran out of their homes to higher ground when the pre-dawn earthquake struck, but they later received text messages saying there was no danger of a tsunami. A massive quake off the coast of Aceh in 2004 triggered a powerful tsunami that killed around 230,000 people in a dozen countries.

Saturday's magnitude 6.2 quake was centred 40 kilometres (24.8 miles) south-southwest of Meulaboh, a coastal city in Aceh province at a depth of 49 kilometres (30.4 miles), the U.S. Geological Survey said.

The Indonesian Meteorology, Climatology and Geophysics Agency measured the earthquake at magnitude 6.4. Variations in early measurements are common.

Indonesia is a seismically active archipelago of 270 million people that is frequently struck by disasters such as earthquakes, volcanic eruptions and tsunamis.

In February, a magnitude 6.2 earthquake killed at least 25 people and injured more than 460 in West Sumatra province. In January 2021, a magnitude 6.2 earthquake killed more than 100 people and injured nearly 6,500 in West Sulawesi province.