ATHENS (AFP) - Twin undersea earthquakes of over magnitude 4.0 jolted Greece on Thursday, the National Observatory said, with no injuries or damage immediately reported.

The first 4.1-magnitude tremor struck at 12.01pm (5.01pm Singapore time), some 47km north of the island of Crete, the observatory said.

Some two hours later, a 5.0-magnitude tremor hit south-east of the coastal town of Pylos in the western Peloponnese at 2.53pm, the observatory said.

Greece is Europe's most seismically active country, and experiences frequent earthquakes, accounting for half of the continent's recorded quakes.

Another earthquake of magnitude 4.4 jolted Athens early on Tuesday morning.