Pope Francis flew deep into the jungle of the Southwestern Pacific island nation of Papua New Guinea on Sunday to visit Catholics living in one of the most remote areas of the world and deliver medical supplies and other aid.

Travelling 1,000 km (620 miles) in a C-130 cargo aircraft provided by the Royal Australian Air Force, Francis arrived with a small entourage in Vanimo, a township of some 12,000 people in the northwestern corner of PNG's main island, with no running water and scarce electricity.

The 87-year-old pope brought hundreds of kilograms of items to help support the local population, said Vatican spokesman Matteo Bruni. They included various medicines and clothing, as well said toys and musical instruments for school children, Bruni said.

The pope is visiting the nation of 600 islands as part of his ambitious 12-day, four-country tour of Southeast Asia and Oceania, the longest of his 11-year-old papacy.

He came to Vanimo at the invitation of local missionaries with the Catholic Institute of the Incarnate Word. They, like Francis, the first pope from the Americas, are from Argentina.

"You are doing something beautiful, and it is important that you are not left alone," Francis told the crowd, which the Vatican estimated at 20,000, of missionaries and Catholic faithful from Vanimo in a meeting outside the town's one-storey, wood-panelled cathedral parish.

"You live in a magnificent land, enriched by a great variety of plants and birds," said the pope. "The beauty of the landscape is matched by the beauty of a community where people love one another".

The Rev. Tomas Ravaioli, one of the missionaries, said he could not believe the pope had actually come to Vanimo. "He is keeping his promise to come," said the priest. "We cannot believe it. At his age he is making an enormous effort."

A sprawling country of mountains, jungle and rivers, PNG is home to more than 800 languages and hundreds of tribes, including dozens of uncontacted peoples.