Pope Francis has opened a landmark synod of bishops from around the world which will review Church teaching on the family and marriage.

The bishops and a small number of lay figures will spend the next two weeks addressing the gulf between what the Church says about issues such as divorce, contraception and pre-marital sex, and what many followers actually do.

The secretary-general of the Synod of Bishops, Cardinal Lorenzo Baldisseri, said the aim is to provide answers to Catholics who are disillusioned by the Church's moral teachings.

He said the synod will not shy away from the difficult questions.

"I think that what this synod will try hardest to do is to give a true answer to problems," Cardinal Baldisseri said.

"This is a real gesture that these questions are noted and will be discussed.

"It will be a message of great beauty – of greatness. And that will be put at people's disposal with all due honesty and sincerity."

No immediate changes are expected to result from the synod, though it will prepare the way for a larger gathering of Catholic clerics next year, which will present the Pope with suggestions that could lead to changes.

First gay Catholic congress to press for change

Coinciding with the synod, gay and lesbian Catholic groups are holding an international congress in Portugal this week as they seek to make their voices heard by the Vatican.

Opening on Monday in the southern resort of Portimao, the three-day event aims to formally federate some 30 associations representing homosexual Catholics from around the world.

Together they intend to press for an "urgent change of attitude from Catholic authorities" towards gay parishioners, said Jose Leote whose group Rumos Novos (New Directions) is organising the event.

The congress will draw up a statement to send to Pope Francis and the nearly 200 bishops meeting for two weeks in Rome.

"Jesus began with 12, and look at what that has become," said Francis DeBernardo, head of the US-based News Ways Ministry, which represents lesbian, gay, bisexual, and transgender (LGBT) Catholics.

Mr DeBernardo intends to act as a bridge between the congress and the synod.

The US group wrote to Pope Francis a few months ago, thanking him for his openness to discussing LGBT issues and urging him to go further.

"I think this will be a major question of the synod," Mr DeBernardo said.

"The topic of homosexuality is so widespread in so many societies and it affects so many people – not only those who are LGBT, but their families, friends, co-workers."

While it is unlikely the Roman Catholic Church will embrace gay marriage, it could send out a signal of compassion by making it clear priests should be ready to baptise the children of same-sex couples.

AFP/Reuters