Pope Benedict XVI's outdoor mass at Fatima has taken place amid heavy rain downpours and low temperatures this afternoon.

Pilgrims flooded the shrine of Fatima ahead of the mass, many having spent the night outdoors on the esplanade and surrounding parks in sleeping bags to make sure they got a place.

Worshippers climbed on statues and stood on the steps leading to the altar of the shrine to get a better view of the 83-year-old pontiff, who was greeted by applause and cheers when he arrived on his white bullet-proof Popemobile.

The mass drew group pilgrimages from 35 nations from around the world, including India, China and Vietnam, according to shrine officials.

'The rain was harder to deal with than the cold. We came to the altar at 4:30 am but there were already lots of people here, we are not as close to it as we would like,' said Isaac Gonzales from Seville in Spain.

A Church spokesman said around half a million people had turned out, more than for Pope Benedict's predecessor Pope John Paul II when he last visited exactly ten years ago.

Portuguese spokesman Manuel Morujao said the faithful wanted to show support for the Pope over his handling of the paedophile priest crisis and that he 'is very much loved'.

Mr Morujao said several factors were responsible for the massive turnout but mainly 'the fact that the image given of the Pope has been unfair. There's been a certain generalisation and the Pope has even been accused of a cover-up,' he said.

'As far the crisis and scandals are concerned, I think that the people wanted to show that they can distinguish between exceptions and the vast majority of their priests,' he said.

'I think that Christians wanted to send a message to say that the Pope, and this one in particular, is very much loved, and to say also that shyness is not a fault, but part of character.'

Pope Benedict has drawn vast crowds throughout his trip to Portugal, where nearly 90% describe themselves as Catholic but less than one-third attend mass every week.

The trip began on Tuesday with an outdoor mass in Lisbon's biggest square.

'What we are searching for is a supplementary blessing. The presence of the Pope increasing the blessing which we already receive here from the Virgin,' said Serge Corenthin who was part of a group of 40 who came from Senegal.

Virgina Gouveia, a 56-year-old cook who attended the mass with a handerkerchief bearing Pope Benedict's image wrapped over her head, arrived in Fatima yesterday after walking from Oliveira do Hospital in central Portugal.

'I was very attached to John Paul II, who was very paternal. But when I look at this Pope I find that he too is capable of leading the Church and sending young people on the right path. He has made me want to stop holding on to the past and to think of the future.' she said.

The Pope himself appeared buoyed by the crowd, telling them of the 'great hope which burns in my own heart and which here, in Fatima, can be palpably felt.'

'I have come to Fatima to pray, in union with Mary and so many pilgrims, for our human family, afflicted as it is by various ills and sufferings,' he said in his homily.

The two-hour ceremony marked the 93rd anniversary of the Virgin Mary's reported apparitions to three shepherd children in 1917.

A statue of Our Lady of Fatima, perched atop of bed of white roses and borne by soldiers, took centre stage behind a procession of bishops before the mass began. Pilgrims threw rose petals at the statue as it passed by.

'People need something that gives them hope, there are many problems in the world and it is not surprising that there are many people here,' said Maria Caldeira, 66.

The pope arrived in Fatima by helicopter from Lisbon yesterday.

Shortly after his arrival he prayed that his priests would be able to avoid the snares of the world and reject the temptations of the devil and said that they should 'not give in to our egoisms, to the snares of the world and the temptations of the devil'.

In a speech to the clergy, he urged them to be wary of 'those situations where there is a certain weakening of priestly ideals or dedication to activities not fully consonant with what is proper for a minister of Jesus Christ.'

'Then is the time to take a firm stand, with an attitude of warm, fraternal love, as brother assisting his brother to remain on his feet.'

Pilgrims in the crowd to hear the Pope yesterday were divided on how the sexual abuse scandal can affect a person's faith.

'I believe that the scandals do have an impact on people's faith, especially on trust for teachers,' said Domingos Silva, a fisherman who walked 160km to reach Fatima.

'I think Pope Benedict's response to these outrageous crimes has been too modest and inefficient to prevent this crisis from reaching the scale it has,' he added.

A 70-year-old Portuguese nun said: 'These scandals should not have an impact on people's faith, but they can harm the Church's reputation if this problem is not tackled properly.'

Pope Benedict has not directly referred to the abuse controversy, which has left the Portuguese Church untainted, since his visit began.

While on the plane travelling to Portugal on Tuesday, the Pope said that the problems the Church faced came not from its enemies, but from sin within the institution itself.

He told reporters onboard that he believed that the interpretation of the third secret revealed by the Virgin Mary to the children at Fatima in 1917 could be enlarged to include the suffering that the papacy and the Church would have to endure as a result of today's sexual abuse crisis.

He also said that justice for the victims of abuse must be a priority. The comments were effectively a reversal of earlier Vatican attempts to blame media sensationalism for the Church's problems.