Many never returned.

Almost 100 years later Belgium's crown prince has marched past those same stone lions - which now stand at the main entrance of the Australian War Memorial in Canberra - to honour the Diggers that died on his country's soil.

Prince Philippe visited the memorial on Friday as part of a week-long visit to Australia.

The future king laid a wreath at the Tomb of the Unknown Soldier and heard the stories of five young Australian men who died on Belgium's battlefields.

He then inspected the lions, which the people of Ypres gave to Australia in 1936 as a sign of gratitude for the sacrifices made in Flanders.

The lions will soon return to the Menin Gate as part of the 100th anniversary commemorations of the battle of Passchendaele, in which thousands of Australians died.

Prince Philippe called it a ''beautiful gesture''.

''A century ago, these lions watched over many young men on their way to the battlefields of Ypres,'' the prince said in a subsequent meeting with officials.

''In 2017 they will once again watch over many young people honouring these men during the commemoration ceremonies.

''As the guardians of peace, they will, for sure, inspire our youngsters to follow the path of solidarity and dedication.''

Defence Science and Personnel Minister Warren Snowdon thanked the prince for his country's co-operation.

''We'll have the whole nation behind these commemorative events,'' Mr Snowdon said, before signing an agreement with Belgian Defence Minister Pieter De Crem on how the countries will co-operate to organise the events.

A total of 12,749 Australian troops are buried or commemorated in Belgium. Some 6190 who have no known grave are commemorated on the Menin Gate Memorial at Ypres. AAP