The quake was recorded at 4:40 pm (1640 GMT) with an epicenter 10 kilometers (six miles) deep in the Atlantic ocean, and 450 kilometersmiles) west of the southwestern point of Cape Sao Vicente.

Meteorological institute seismologist Fernando Carrilho characterized the activity as normal for the region.

"It is linked to the interaction of the Eurasian and African continental plates,"he told public television.

Witnesses reported especially strong shaking on the top floors of buildings.

At the end of December two earthquakes measuring 4.4 and 4.5 on the Richter scale occurred within half an hour of each other.

The meteorological service recorded some 20 earthquakes last year, none of which caused injuries or damage.