Pope Francis touched down in Singapore on Wednesday, the last stop of a 12-day four-nation Asia-Pacific trip aimed at boosting the Catholic Church's standing in the world's most populous region.

Crowds waved Vatican and Singapore flags as Francis's plane arrived at the city-state's Changi Airport.

The 87-year-old pontiff has defied doubts about his health during a journey that has taken him from a Jakarta grand mosque to a remote jungle of Papua New Guinea.

In recent years, the ailing pope has undergone hernia surgery and has been plagued by respiratory issues. He now relies on a wheelchair, walking sticks or aides to get around.

But throughout the trip, he has carried out dozens of public engagements, energised congregations through impromptu call-and-response and repeatedly sat for hours in the brutal tropical heat.

In East Timor, he held a mass for 600,000 faithful -- almost half the nation's population -- before flying on Wednesday to finance hub Singapore.

About 30 percent of Singaporeans are Buddhist, 20 percent have no religion and the rest are a mix of Catholic, Protestant, Taoist and Hindu.

Erik Hon, a 45-year-old Buddhist fintech worker, said he was "delighted" by the pope's visit, hoping it would "spread the message of love, peace and unity to all stripes of humanity".

"He sought to reach out to the marginalised and to deepen dialogue between different faiths and those without any faith."

Like many businesses, Francis is likely to use Singapore as a platform to reach the rest of the region and the world.

"The pope will most likely continue to underline a number of global issues that are not specific to a single country," said Michel Chambon, an expert on Christianity in Asia at the National University of Singapore.

"The importance of inter-religious harmony and international peace, the need for a more resilient and equitable development as well as the necessity for stronger efforts to fight climate change," he said, suggesting familiar themes for this leg of the pope's trip. (AFP)