JAKARTA, Aug. 20 (Xinhua) -- At least 12 people have been killed and dozens others injured as two quakes, measuring 6.5 and 6.9 magnitude respectively rocked Lombok Island in central Indonesia again on Sunday, disaster agency officials said on Monday.

The jolts came after earlier quakes of 6.4 and 7.0 magnitude which struck off the island on July 27 and Aug. 5 respectively, spokesman of national disaster management agency Sutopo Purwo Nugroho said.

Most of the victims were hit by debris and falling blocks of concrete, he said.

The 6.5 magnitude quake jolted at 11:10 a.m. local time (0410 GMT) with the epicenter at 32 km East Lombok of West Nusa Tenggara province in western parts of the island with depth of 10 km, the agency said.

The 6.9 magnitude one struck at 9:56 p.m. local time (1456 GMT) with the epicenter at 30 km northeast East Lombok district of West Nusa Tenggara province with a depth of 10 km, it said.

No tsunami warning was issued.

The 6.9 magnitude quake killed 10 people and devastated 151 houses, the spokesman noted.

"When the quakes were striking many folks were in makeshift encampment, accordingly the jolts did not result in many victims," he told Xinhua in a text message.

The two strong quakes on Sunday wounded about 40 people across Lombok island, head of emergency unit of the disaster agency in West Nusa Tenggara province Agung Pramudja told Xinhua by phone.

The latest figures brought the total death toll of the quake since July 27 to at least 472, according to the disaster agency.

Indonesia is prone to quake as it lies on a vulnerable quake-hit zone of "the Pacific Ring of Fire."