A magnitude-6 earthquake shook the interior of Papua New Guinea on Wednesday, two days after another magnitude-7.5 earthquake in the same region caused landslides that left at least 31 people dead and another 300 injured.

The US Geological Survey (USGS), which records seismic activity around the world, placed the hypocenter of the earthquake at a depth of 10 km and its epicentre at 90 km from Mendi, the provincial capital of the Southern Highlands Province.

At least 13 people were killed in Mendi after the first earthquake and another 18 in the regions of Kutuku and Bosave.

The police said that up to 400,000 people in four provinces had been affected by the quakes, which hit the region early Monday.

The Ok Tedi Mine and ExxonMobil-operated gas conditioning plant in Hides gas field, Hela Province, had been shut down as a precautionary measure to assess possible damage to the facilities.

The country is located on the so-called Pacific Ring of Fire, an area of intense seismic and volcanic activity due to friction between tectonic plates.