An earthquake measuring 6.1 on the Richter scale struck southeast of the Pacific island nation of Tonga, the US Geological Survey (USGS) said.

The quake hit 171.12 miles southeast of the capital Nuku'alofa at a depth of 66km.

Earlier, the USGS tweeted the preliminary reading of the quake to be 5.8.

The part of the South Pacific Ocean around Tonga is one of the most seismically active areas of the world, the USGS said, due to convergence between the Australia and Pacific tectonic plates.

Last March, a magnitude 6.0 earthquake struck between Tonga and Fiji.

Ecuador earthquake in pictures Show all 16 1 /16 Ecuador earthquake in pictures Ecuador earthquake in pictures Ecuador earthquake in pictures Ecuador earthquake in pictures Ecuador earthquake in pictures Ecuador earthquake in pictures Ecuador earthquake in pictures People stand amongst the rubble of fallen homes in Manta, after a powerful 7.8-magnitude earthquake struck Ecuador Ecuador earthquake in pictures A collapsed bridge after a 7.8 magnitude earthquake hit the city of Guayaquil, Ecuador, late 16 April 2016. At least 77 people were killed and hundreds injured in an earthquake affecting the Ecuadoran northern coastal region. EPA/Freddy Constante Ecuador earthquake in pictures Police officers stand next to a collapsed overpass in Guayaquil, Ecuador, Saturday April 16 2016. The strongest earthquake to hit Ecuador in decades flattened buildings and buckled highways along the country's coast, killing at least 41 people and causing damage hundreds of kilometres away from the epicenter in the capital and other major cities. AP Photo/Jeff Castro Ecuador earthquake in pictures Rescue workers work to pull out survivors trapped in a collapsed building after a huge earthquake struck, in the city of Manta early on April 17 2016. At least 41 people were killed when a powerful 7.8-magnitude earthquake struck Ecuador, destroying buildings and sending terrified residents dashing from their homes, authorities said late on April 16. Ariel Ochoa/AFP/Getty Images Ecuador earthquake in pictures People walk near a damaged house after an earthquake struck off the Pacific coast in Manta, Ecuador, April 16 2016. REUTERS/Paul Ochoa Ecuador earthquake in pictures People stand on the debris of a building after an earthquake struck off the Pacific coast in Manta, Ecuador, April 16 2016. REUTERS/Paul Ochoa Ecuador earthquake in pictures People gather next to a collapsed house in Guayaquil on April 17, 2016. At least 41 people have been killed by the powerful earthquake that struck western Ecuador on Saturday and the toll will likely rise further, the country's Vice President Jorge Glas said. JOSE SANCHEZ L/AFP/Getty Images Ecuador earthquake in pictures People stand amongst the rubble of fallen homes in Manta on April 17, 2016, after a powerful 7.8-magnitude earthquake struck Ecuador on April 16. At least 77 people were killed when a powerful 7.8-magnitude earthquake struck Ecuador, destroying buildings and a bridge and sending terrified residents scrambling from their homes, authorities in the Latin American country said on April 17. JUAN CEVALLOS/AFP/Getty Images Ecuador earthquake in pictures View of rubble after a 7.8-magnitude quake in Portoviejo, Ecuador on April 17, 2016. At least 77 people were killed when a powerful earthquake struck Ecuador, destroying buildings and a bridge and sending terrified residents scrambling from their homes, authorities said Sunday. JUAN CEVALLOS/AFP/Getty Images Ecuador earthquake in pictures People help clean rubble after a 7.8-magnitude quake in Portoviejo, Ecuador on April 17, 2016. At least 77 people were killed when a powerful earthquake struck Ecuador, destroying buildings and a bridge and sending terrified residents scrambling from their homes, authorities said Sunday. JUAN CEVALLOS/AFP/Getty Images Ecuador earthquake in pictures People watch a collapsed house in Guayaquil on April 17, 2016. At least 41 people have been killed by the powerful earthquake that struck western Ecuador on Saturday and the toll will likely rise further, the country's Vice President Jorge Glas said. JOSE SANCHEZ L/AFP/Getty Images

Another powerful earthquake hit Ecuador, leaving at least 77 people dead.