A shallow and moderately strong 5.9 quake struck about 40 kilometres off Sumba, an island of some 750,000 people.
As the desperate search for survivors of the Sulawesi tsunami continues, two quakes struck in quick succession off the southern coast of Indonesia's Sumba island on Tuesday morning, the United States Geological Survey reported.
A shallow and moderately strong 5.9 quake struck about 40 kilometres 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 kilometres.
There were no immediate reports of serious damage, although one hotelier reported that guests ran out of his hotel in panic.
The death toll in the Sulawesi town of Palu continues to rise towards 1,200 with many others still missing under collapsed buildings. The bodies of 34 students were found in a church on Tuesday after a mudslide engulfed the church in which they were meeting.
Heroic stories are emerging from the devastating earthquake and tsunami that destroyed the town.
The ABC reported Anthonius Gunawan Agung, a 21-year-old airport worker, was the only one left in the control tower at Mutiara Sis Al Jufri Airport in Palu when the quake hit after his colleagues had all run for their lives.
Agung stayed to make sure Batik Air Flight 6321 was able to take off safely, even as the tower began to sway and crack.
“He gave clearance for this flight, and if he left his post before the plane was airborne, hundreds of people inside the plane might be in danger,” Yohannes Sirait, spokesman for Air Navigation Indonesia told the ABC.
Part of the reason for the slow delivery of supplies to Palu is due to the damage to the airport, where only one runway is operational. On Monday, the airport was forced to close temporarily as hundreds of people flocked to the airport to beg the military to evacuate them or give them food.