Thousands of Catholics waving flags from around the world packed St. Peter's Square on Sunday to hear Pope Francis deliver his inaugural Angelus.

The new pontiff gave his Angelus, or noon blessing, from the papal apartment window, speaking to more than 200,000 worshippers in the square four days after his election as pope.

"Dear brothers and sisters, good morning," he said in Italian, drawing cheers from the crowd.

During the 15-minute address, he focused on forgiveness.

"Never forget this: The Lord never tires of forgiving us," he said. "Have you thought about the patience that God has with each of us?"

He made the historic address after celebrating Mass at Sant'Anna parish in Vatican City earlier Sunday.

In a rare move for a pope, Francis spontaneously walked out from Vatican territory to greet cheering well-wishers outside Sant'Anna Gate.

"Francesco, Francesco!" the crowd chanted.

Also on Sunday, the pope sent out his first message from the papal Twitter account: "Dear friends, I thank you from my heart and I ask you to continue to pray for me. Pope Francis."

In his first week as pontiff, Francis has enjoyed global fanfare as the first Latin American pope and the first Jesuit pope in modern times.

The official Mass to inaugurate Francis as the bishop of Rome -- and leader of the world's 1.2 billion Roman Catholics -- will take place Tuesday.

A church 'for the poor'

The new pope explained his choice of the name Francis in a meeting with journalists Saturday and discussed how he wished for a church that was both poor and "for the poor."

Francis, who before he became pope was Cardinal Jorge Bergoglio, said a fellow cardinal from Brazil had told him "Don't forget the poor" as the votes stacked up in his favor.

"Right away, with regard to the poor, I thought of St. Francis of Assisi, then I thought of war," he told the assembled journalists. "Francis loved peace and that is how the name came to me."

He had also thought of St. Francis of Assisi's concern for the natural environment, he said, and how he was a "poor man, a simple man, as we would like a poor church, for the poor."

St. Francis of Assisi, who gave up his own wealth and prestige, is revered among Catholics for his work with the poor.

A blessing for all

The new pope concluded the meeting with press -- which did not include questions -- with a blessing for all the journalists present and their families.

Francis acknowledged that not all those present were Catholic, saying he gave them his blessing "knowing that you are of different religions, because all of you are children of God."