Pope Francis returned to Rome on Tuesday after a four-day trip to Japan, including visits to Nagasaki and Hiroshima where he delivered powerful anti-nuclear appeals and urged efforts for peace.

During the first papal visit to Japan in 38 years, the pope called for the elimination of nuclear weapons in addresses in the two atomic-bombed cities, and held meetings with Emperor Naruhito and Prime Minister Shinzo Abe in Tokyo.

On Tuesday morning, the pope gave thanks to "the entire Japanese people for the kind reception and welcome" during his "short and very intense" stay in the country, delivering his speech to some 700 people at Sophia University in Tokyo.

"Despite the fact that Christians are a minority (in Japan), their presence is felt," the pope said. "I myself have witnessed the general esteem in which the Catholic Church is held, and I hope that this mutual respect may increase in the future."

He also held some private meetings with Jesuits at the university, a Jesuit school.

After arriving in Rome, the pope also tweeted in Japanese, "I express deep gratitude to all the people of Japan."

On Sunday, the 82-year-old Argentine pope gave speeches in Nagasaki and Hiroshima, stressing a world without nuclear weapons is "possible and necessary," and saying the use of such weapons is a "crime" against humanity and nature.

On Monday in Tokyo, the pope met with victims of the March 2011 earthquake and tsunami as well as the Fukushima nuclear crisis caused by the natural disaster, and held a mass at Tokyo Dome attended by about 50,000 Catholic adherents.

Elected as Roman Catholic pontiff in 2013, Francis is the first Jesuit to become pope. Saint Francis Xavier, a Jesuit missionary, first introduced Christianity to Japan in 1549.

The papal visit came roughly five years after Abe asked the pope to visit Japan during a 2014 meeting in Vatican City.

John Paul II, who in February 1981 made the first papal trip to Japan, pushed for the elimination of nuclear weapons during a visit to Hiroshima and Nagasaki amid heightened tensions between the United States and the Soviet Union over the deployment of intermediate-range nuclear missiles.