Pope Francis departs Rome for 12-day tour across Southeast Asia

Pope Francis left Rome on Monday for Jakarta, where the 87-year-old leader of the global Catholic Church will start an ambitious 12-day tour to four countries in Southeast Asia.

The flight carrying the pope and his entourage left Fiumicino airport for an overnight flight of more than 13 hours to the Indonesian capital.

The pope will be in Indonesia until Friday. He is then scheduled to visit Papua New Guinea, East Timor and Singapore before returning to Rome on Sept. 13.

Francis, who has stressed the importance of environmental issues throughout his 11-year papacy, is expected to urge global action on climate change during the voyage.

Each of the countries on his tour is facing dangers from the warming global climate, including rising sea levels and increasingly severe and unpredictable heat waves and typhoons.

Francis is set to travel nearly 33,000 km (20,500 miles) throughout the visit, and will headline more than 40 events. It is the longest trip yet by the pontiff, who now regularly uses a wheelchair due to knee and back pain and has had bouts of ill health.

He was in a wheelchair as he boarded the flight on Monday, using a mobile lift to gain access to the aircraft.

At a press briefing on Friday, the Vatican said it was not taking any unusual medical precautions for the pope on this trip.

"We are taking the same precautions that we always take," said Matteo Bruni, director of the Vatican press office.