An undersea earthquake with a magnitude of 6.1 struck south of Indonesia's Bali today, the European earthquake monitoring agency EMSC said, causing some residents and visitors on the tourist island to briefly rush out of buildings.

There were no immediate reports of damage or casualties from the quake and there was no tsunami warning issued by the Hawaii-based Pacific Tsunami Warning Centre.

The epicentre was 102 km southwest of the island's capital, Denpasar, and was 100 km deep, the EMSC said.

The United States Geological Survey recorded the quake with a preliminary magnitude of 5.7.

One resident said people in Denpasar ran out of their boarding houses in pyjamas after feeling the quake.

A Twitter user with the handle Indounik in the city of Ubud on Bali said the quake was "strong enough to make me adopt the drop, cover & hold approach recommended to survive a quake".

Another Twitter user, Marc van Voorst, described the quake as feeling like "a heavy truck or a train passing by at close range". He said there was no panic, even though his hotel in the Uluwatu area shook quite a bit.

The quake could also be felt in other cities on the neighbouring islands of Lombok and Java, Indonesia's meteorology and geophysics agency said in a statement.

Indonesia suffers frequent earthquakes, sometimes causing tsunamis because it lies on the seismically active Pacific Ring of Fire.

Its Moluccas islands were hit by a powerful 7.2 quake on Sunday that killed at least two people and prompted hundreds to flee their homes.

The most devastating tremor in recent Indonesian history was on Dec 26, 2004, when a magnitude 9.5 quake triggered a tsunami that killed around 226,000 people along the shorelines of the Indian Ocean, including more than 126,000 in Indonesia.

A tsunami also hit the city of Palu in Sulawesi last year, killing thousands.

- Reuters