A ceremony is under way in Olympia, Greece, to light the Olympic flame ahead of the start of the torch relay and the London 2012 Games, BBC reported.

The flame is kindled by a "high priestess" who captures the morning sun's rays in a parabolic mirror.

The ceremony comes amid political and economic turmoil in the home of the Ancient Olympics, where a week-long leg of the relay will be held.

The flame flies to Britain on 18 May for a 70-day relay around the UK.

Locog Chairman Lord Coe, International Olympic Committee president Jacques Rogge and Hellenic Olympic Committee president Spyros Capralos are in Olympia for the moment marking the countdown to London 2012.

The lighting ceremony takes place in front of the ruins of the Temple of Hera.

The flame - an Olympic symbol meant to represent purity because it comes from the sun - is placed in an urn and taken to the stadium where the ancient Olympic Games were staged.

There, it will light the London 2012 torch of Liverpool-born Greek world champion 10km swimmer Spyros Gianniotis, who will carry it on the first leg of the relay around Greece.