MANILA: Pope Francis will immerse himself in some of Asia's most fervent Catholicism during a trip to the Philippines and Sri Lanka starting Tuesday, with millions of devotees set to turn out.

The Argentinian pontiff with a man-of-the-people reputation could attract one of the biggest gatherings ever for a pope during an open-air mass in the Philippine capital of Manila.

The January 18 event may draw up to six million people, offering a pulsating example of Asia's status as a dynamic growth region for the Catholic Church — but also creating a security nightmare.

The pope's trip, which begins in Sri Lanka, comes just five months after he visited South Korea, signalling the huge importance the Vatican places on Asia and its potential for more followers.

“This second trip to Asia ... is a message in itself for this great continent. It is necessary to have the pope return to this important part of the world,” Vatican spokesman Father Federico Lombardi said as the 78-year-old pontiff prepared for the week-long visit.

In Sri Lanka, the pope will preach reconciliation as the majority Buddhist nation of 20 million people continues to endure ethnic conflict following the end in 2009 of nearly four decades of civil war that pitted separatist Tamils against Sinhalese.