At least 12 people were killed and 25 others injured on the Indonesian islands of Lombok and Sumbawa after two strong earthquakes struck the former island, Indonesian officials said Monday.

Ten of the 12 died as a result of the magnitude 6.9 quake that occurred at 10:56 p.m. Sunday at a depth of about 20 kilometers, centered on the northeastern part of the island. The two other victims perished when a magnitude 6.3 quake hit Lombok at 12:10 p.m. at a depth of 7.9 km.

Almost 2,000 houses were also damaged or destroyed.

Efforts to assess the situation in East Lombok have met difficulties because communications with the area were cut off and some roads were damaged by the quakes, National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said.

At least 101 smaller quakes with magnitudes as high as 5.8 had occurred as of 1:25 a.m. Monday, according to the Jakarta-based Meteorology, Climatology and Geophysics Agency.

Both temblors were strongly felt on Lombok as well as on Bali, a resort island west of Lombok, sending people into a panic, according to Sutopo.

Some of the victims of the Sunday quake were found in the island's East Lombok Regency, which is believed to be the area most affected by the quake, while the others were found on nearby Sumbawa Island, Sutopo said.

"Emergency efforts have intensified," the spokesman said.

The 12:10 p.m. quake caused landslides on the slopes of Mt. Rinjani, a 3,726-meter active volcano on Lombok that is popular among international and local tourists.

(Rescuers search for the missing on Aug. 8 following an earlier quake on Lombok Island)

The temblors came two weeks after a magnitude 6.9 quake struck Lombok's northwest, killing at least 471 people, according to the latest count. A week earlier, the island had been hit by a magnitude 6.4 earthquake that killed 17 people.

Indonesia sits in one of the most active seismic regions in the world, the Pacific Ring of Fire -- an area in which a large number of earthquakes and volcanic eruptions occur.