A strong 6.1-magnitude earthquake hit off Indonesia late on Monday, seismologists say, but no tsunami alert was issued and there were no immediate reports of injuries or damage.

The quake struck at 11.12pm (0212 AEST) at an underwater depth of 15 kilometres, south of the main island of Java, according to the US Geological Survey.

Earthquakes are common in Indonesia because it sits on the so-called Pacific Ring of Fire, where several tectonic plates converge.

At least 100 people were likely killed by a major 7.0-magnitude quake that rocked Java last week, an official said earlier on Monday, and over 88,000 people were left homeless.

Authorities have confirmed 74 people were killed in last Wednesday's quake, which also struck off the south coast of Java.

A 7.7-magnitude quake triggered a tsunami off southern Java in 2006, killing 596 people and displacing about 74,000.

A massive quake off the coast of the island of Sumatra in 2004 triggered a catastrophic tsunami that killed more than 200,000 people around Asia, including 168,000 in Indonesia.