As if beamed on by the ancient Greek god of the sun Apollo, high priestess Thalia Prokopiou lifted a blazing torch lit from rays of the sun via a polished steel mirror.

"Apollo, sun god and god of the idea of light, send us your rays to light the torch for Athens," Prokopiou intoned as the torch burst into flame among archaeological ruins at Olympia, birthplace of the Games.

She carried the torch to Greek javelin champion Costas Gatzioudis who was the first torch bearer in an unprecedented global relay that for the first time will take in the five continents represented by the Olympic Rings.

The journey of the metal and wood torch, carved in the shape of an olive leaf, will last 78 days and for the first time travel to Africa and South America.

With 141 days to go until the August 13 opening ceremony, the torch ceremony, even if briefly, pushed to the background worries about delays in building Games venues and security worries because of international terrorism.

"It was in Olympia everything began and today everything is going to begin for Athens 2004," International Olympic Committee chief Jacques Rogge said.

"What better image of universality can the Olympic Games offer than to organise the first global Olympic relay.

"Whether male or female, young or old, able bodied or disabled, high level athlete or amateur, employer or employee, famous or unknown, whether we live in a rich or disadvantaged country, the flame will unite us all."

The Olympics were first held in 776 B.C. and staged every four years until Roman Emperor Theodosius abolished them in 393 A.D. because he judged them pagan.

UNPRECEDENTED SECURITY

They were reborn in Athens in 1896 by a group headed by a French baron, Pierre de Coubertin.

There was unprecedented security at Olympia for the crowd of 10,000 with bomb squads, sniffer dogs and police marksman swarming over the idyllic setting of gentle grassy slopes dotted with spring wildflowers.

Several thousand more locals and foreign tourists broke through police barriers, even wading over a stream to watch.

Vehicles, except for security forces, were banned within a three kilometre radius of the ceremony.

"Security is appropriate for this event. Yes its larger than previous years but that's what is appropriate," Greek Public Order Minister George Voulgarakis told Reuters.

Athens Games chief Gianna Angelopoulos and Greece's new prime minister Costas Karamanlis were present on Greece's independence day, a national holiday, for a ritual, introduced prior to the 1936 Berlin Olympics.

"Today we light the torch that will truly light the world," said Angelopoulos, who has been mainly credited with overcoming months of delay in building works.

In their bid to catch up, Games organisers in the past week have scrapped plans for a roof over the main swimming pool, trimmed back landscaping of the marathon start and postponed a train extension for the capital.

The main remaining worry is a roof to be built over the main stadium.

Rogge said thanks to a "new energetic Greek government" the IOC believed Greece could make up time.

"There's a lot to be done but our experts say there's enough time. So yes I am very optimistic," he told Reuters.

Other prominent torch runners on the first few days include Prince Albert of Monaco, who took part in former Winter Olympics, pole vault Olympic gold medallist Sergei Bubka and Manuel Estiarte, Spain's water polo player who competed in six Olympics.