JAKARTA, Oct. 2 (CGTN) -- The death toll has risen to 1,234 after a powerful 7.5-magnitude earthquake and tsunami hit Indonesia on Friday, the national disaster management agency said Tuesday.

Twin quakes struck off the southern coast of Indonesia's Sumba island on Tuesday morning, according to the United States Geological Survey (USGS).

A shallow and 5.9-magnitude quake struck at 23:59 GMT, around 40 km off Sumba, an island of some 750,000 people. It was followed up some 15 minutes later by a stronger 6.0-magnitude quake in the same area at a depth of 30 kilometers. But no tsunami alert was issued.

Indonesian rescue workers discovered 34 bodies of students who were killed when a mudslide caused by Friday's quake on Sulawesi island engulfed their church, a local rescue official said. Indonesian Red Cross spokeswoman Aulia Arriani told the media Tuesday that 86 students had initially been reported missing from a Bible camp at the Jonooge Church Training Center in Sigi Biromaru district.

A two-meter-high (six-feet-tall) tsunami swept through Palu, home to around 350,000 on Sulawesi island, at dusk soon after the tourist resort was rocked by a 7.5-magnitude earthquake that had a depth of 10 kilometers.

"Bodies of victims were found in several places because they were hit by the rubble of collapsing buildings or swept by the tsunami, but we are still collecting data," said Sutopo Purwo Nugroho, spokesperson for the National Disaster Management Agency.

Videos on social media show people screaming and fleeing in panic among the ruins of buildings.

The quake and tsunami caused a power outage that cut communications around Palu. On Saturday, authorities were still having difficulties coordinating rescue efforts without power and communications as the area was rocked by aftershocks.

The main airport in Palu was shut down after the tsunami struck and is expected to stay closed for at least 24 hours.

Indonesia sits on the Pacific Ring of Fire, which is the line along tectonic plates that circles the entire Pacific Rim where frequent quakes and volcanic eruptions occur.

In August, a series of major quakes killed over 500 people on the tourist island of Lombok and destroyed dozens of villages along its northern coast.