REYKJAVIK (AFP) - A powerful earthquake on Wednesday (Feb 24) rocked southwestern Iceland, including the capital Reykjavik, triggering increased volcanic activity but causing no serious injuries or damage, authorities said.

The epicentre of the quake was located near Mount Keilir, a small mountain of 378 metres on the Reykjanes peninsula, some 30km south of Reykjavik, authorities added.

The US Geological Survey measured one tremor at a magnitude of 5.6 around 4km east of the fishing port of Grindavik.

The Icelandic authorities, meanwhile, recorded a 5.7 magnitude tremor at 1005 GMT (6.05 pm Singapore time).

Numerous tremors were felt after the quake, including 12 which registered above 4.0, and were continuing at midday, according to AFP's correspondent in the capital.

"It's an intense activity zone, we are well aware of that, but I've never experienced or felt so many strong earthquakes in such a short period of time (in Reykjavik), it's unusual," Kristin Jonsdottir, earthquake hazards coordinator at Iceland's Meteorological Office (IMO), told public broadcaster RUV.

The IMO switched from green to yellow the colour code for the aviation sector over the Krysuvik volcano system where the quake occurred, indicating that the "volcano is experiencing signs of elevated unrest above known background levels".

There were, however, no signs of a volcanic eruption yet.

The last eruption in this volcanic system was in the 12th century.

The Reykjanes peninsula, located on a tectonic fault, has been rocked by numerous earthquakes for more than a year.

The most recent large one occurred in October, measuring 5.6.