"The Church calls on all its members to renew themselves which constitutes a fight, a spiritual battle, because the evil spirit wants us to deviate from the road towards God," he said from his balcony overlooking tens of thousands of faithful gathered in St. Peter's Square.

Local authorities said a crowd of more than 100,000 people had turned out to see the 85-year-old pope, who announced Monday that he would step down on February 28 after eight years in office due to advanced age.

Many of the faithful waved flags and held up banners saying "grazie" or "danke", the words for thank you in Italian and the pope's native German.

The pontiff thanked the crowd for turning out in such large numbers, calling it a "sign of affection and spiritual closeness", and the onlookers responded by calling out "viva il papa" (long live the pope).

Benedict is only the second pontiff to resign of his own free will in 2,000 years.