Pope Francis arrived in Seoul on Thursday for his first trip to Asia since he became pontiff in March 2013, with North Korea firing rockets into the Sea of Japan shorty before the pontiff's landed.

The last rocket was fired 35 minutes before Pope Francis was due to land, Australia Network News reported.

"North Korea fired three short-range projectiles into the East Sea (Sea of Japan)," a South Korean defence ministry spokesman said.

The Pope was greeted at an air base in southern Seoul by South Korean president Park Geun-hye along with a delegation of South Korean Catholics that included two North Korean defectors.

Francis will take part in the 6th Asian Youth Day and beatify 124 Korean martyrs during his five day visit to South Korea which has five million Catholics.

A South Korean bishop preceded his visit with a call for understanding and tolerance as Francis flies in for the 6th Asian Youth Day and the beatification of 124 Korean martyrs.

In a recent message, Cheju Bishop Peter Kang U-il listed the ills plaguing South Korea, saying that among the problems everyday Koreans face, the lingering threat to peace is the Pope's chief concern.

"The Holy Father in my opinion chose Korea in the Far East as the first destination of his apostolic visit to the continent of Asia, because he wanted to pray together with us for the peace of the Korean peninsula as well as for this continent as a whole," said Kang U-il, president of the Korean Bishops' Conference.

"I hope that we can embrace with each other in the spirit of tolerance and harmony in full accord with the 'love and hope,' which the Holy Father wants to communicate to us," he said.

"In this regard, I also hope that the seeds of reconciliation and peace will sprout vigorously on this land."

The bishop said he sees Francis' visit to Seoul as a reminder of the missionary nature of the priesthood.

He likened the upcoming visit to that of the missionary journeys of St. Paul, who the bishop said traveled to local churches to spread the Gospel and reenergize the faithful there.

He also expressed solidarity with the protesting relatives of the victims of the Sewol ferry disaster. He asked the National Assembly to pass the special law that forms an independent investigating body that will look into the tragic incident that claimed some 300 lives.

The protesters are on a hunger strike at Gwanghwamun Plaza, where the Pope is scheduled to hold a beatification mass for the Korean martyrs.

The victims say they will not yield in giving up their space for the mass, which church officials anticipate to draw a million believers.