Pope Benedict opened a major Vatican meeting yesterday by decrying a modern culture so devoid of faith that some people were declaring God "dead" and entire nations were losing their identity.

The 81-year-old German Pope made his comments in the homily of a Mass opening a month-long synod of Roman Catholic bishops from around the world who will be discussing God's message through Scripture.

He said nations that were "once rich in faith" were now "losing their identity under the harmful and destructive influence of a certain modern culture".

Since his election in 2005 the Pope has been condemning a loss of Christian identity in most developed countries in Europe and has recently been speaking out about the need to re-inject moral values into Europe's political arena.

"There are those, who, after deciding that 'God is dead', declare themselves to be 'god' and the artisan of their own destiny, the absolute master of the world," he said.

Attempts to "brush God aside" lead to arrogance of power, selfishness, injustice, exploitation and violence, he said at the St Paul Outside the Wall Basilica in Rome.

"When men proclaim themselves to be absolute masters of themselves and sole masters of creation, can they truly build a society where freedom, justice and peace reign?," he said.

The synod, whose formal work begins today, will be discussing scripture and will break new ground when Rabbi Shear-Yashuv Cohen becomes the first Jew to address such a Vatican gathering.

But it has been marred by Beijing's denial of permission for Catholic bishops to travel to Rome for the event.

China's communist government does not allow its Catholics to recognise the Pope's authority and forces them to be members of state-backed Catholic organisation. China's eight to 12 million Catholics are split between the officially approved church and an "underground" one loyal to the Pope.

The lack of participation from China came as a surprise because there had been signs of improved relations this year.