Pope Benedict has called gay marriage and abortion “dangerous threats to the common good” during a visit to Portugal.

The pontiff is on a four-day visit to the country and gave a Mass today to 500,000 people at Fatima, which is considered the Portuguese Lourdes.

Fatima is one of the most revered sites in Catholicism after three shepherd children claimed in 1917 to have seen a vision of the Virgin Mary. Catholics flock to the site in search of miracle cures and to worship there.

Addressing followers today, the Pope called for pastoral action to tackle abortion and same-sex marriage, which he called “some of today’s most insidious and dangerous threats to the common good”.

He called abortion a “tragedy” and urged for protection of the “family based on the indissoluble marriage between a man and a woman”.

Portugal approved gay marriage earlier this year. In January, speaking just after Portugal’s parliament voted in favour of the move, the Pope called it an “attack” on the natural differences between men and women.

He recently criticised gay rights measures contained in Britain’s Equality Act. He said measures designed to ensure churches were not discriminating when hiring staff were against “natural law”.

Following his attack, the government backed down on pushing the measures through.

The Pope is due to visit the UK this September for four days, although protests have already been held by groups angry at his stance on gay rights, abortion, women and contraception.

In an end-of year address in 2008, he said that the existence of gay people threatens humanity as much as the destruction of the rainforests does and that “blurring” genders through acceptance of transgender people would kill off the human race.

He has also attacked the use of condoms to tackle HIV, saying they may make the problem worse.