Rescuers are searching for survivors of a 6.1-magnitude earthquake in the north Sumatran province of Aceh in Indonesia.

Officials say 24 people have been killed and 249 injured. Unofficial reports speak of 41 deaths. Many of the causualties have been caused by landslides.

Six children are reported to be among the dead; they were crushed to death when a mosque collapsed. Fourteen children are believed to be trapped in the rubble.

Yesterday’s quake struck at a depth of just 10 kilometers (6 miles) and was centered 55 kilometers (34 miles) west of the town of Bireun in a mountainous area on the western tip of Sumatra island.

It was felt in Medan, the capital of neighbouring North Sumatra province.

Reports say about 1,500 houses and other buildings were damaged. There have been two major aftershocks measuring 5.2 and 5.3 on the Richter scale.

Hundreds of people slept outdoors on Tuesday night, afraid to return to their homes.

According to Earthquake-Report, there is havoc at the epicenter and landslides are hampering rescue and relief efforts.

Indonesia is located on the Pacific Ring of Fire, an arc of volcanoes and fault lines encircling the Pacific Ocean, so is prone to seismic upheaval.

Earthquake-Report gives details: “This earthquake happened along the extremely dangerous Great Sumatra Fault. The island of Sumatra is located in a highly seismic area of the world. In addition to the subduction zone and the associated Sunda Arc off the west coast of the island, Sumatra also has a large strike-slip fault, the so-called Great Sumatran Fault, running the entire length of the island.

“This fault zone accommodates most of the strike-slip motion associated with the oblique convergence between the Indo-Australian and Eurasian plates. The fault ends in the north just below the city of Banda Aceh, which was devastated in the 2004 Indian Ocean earthquake. After the December 2004 earthquake, pressure on the Great Sumatran Fault has increased tremendously, especially in the north.”

In 2004, a magnitude-9.1 earthquake off Aceh triggered a tsunami that killed 170,000 people in the province and tens of thousands more in countries around the Indian Ocean.

In April last year an 8.6-magnitude quake struck 431 kilometres off Banda Aceh, prompting a tsunami alert.

Five people died and seven were injured in Aceh in the quake and aftershocks.

In September 2009, a major quake near Padang city on Sumatra killed more than 1,000 people.