Pope Benedict XVI has arrived for his first state visit to his native Germany, facing an increasingly secular country still grappling with a church sex abuse scandal.

Earlier, he told reporters on his plane from Rome that he could understand those leaving the Catholic Church due to the sexual abuse scandals of recent years.

Benedict also said he had nothing against the planned demonstrations in protest at his visit, so long as they were civil.

"I can understand that in the face of such reports, people, especially those close to victims, would say 'this isn't my church anymore'," he told reporters.

"There are many reasons for people leaving the church in the context of a secular society. Leaving the church is generally the final step along a long path of distancing oneself from the church," he said.

German Christians are almost exactly divided between Catholics and Protestants and official statistics show that members of both faiths are leaving the church in droves.

Observers put this down, in part, to revelations last year of widespread child molestation by German priests over the last several decades, with top archbishop Robert Zollitsch admitting the church had "failed" in its response.

The Pontiff has a gruelling schedule with 18 sermons and speeches during his 21st trip abroad and is likely to be met with a combination of apathy and protests, as well joy from thousands of faithful Catholics.