PORT MORESBY -- Pope John Paul II arrived in Papua New Guinea on Monday, one day after millions of Catholics turned out in a stunning demonstration of their faith at a Mass to mark World Youth Day in the Philippine capital, Manila.


In Port Moresby, the Papua New Guinean capital, the Pope was greeted by thousands of islanders, including warriors in feathered headdresses, as he rode by in an open pickup truck.


Later he led about 300 parishioners in prayer inside a sweltering church cooled by a single fan.


The size of congregation was in stark contrast to the millions who had attended the service in Manila the day before. Vatican officials said the turnout was the biggest for a papal event, surpassing even the welcome the Pontiff has received in his native Poland.


Papal spokesman Jaoquin Navarro-Valls said John Paul was delighted with the response in the Philippines, Asia's only mainly Catholic country.


"He is delighted. It is his first trip in such a long time and he has found this kind of reception," said Navarro-Valls, who estimated the number of people at four million.


The Pope, 74, on his first major overseas tour since breaking a leg last year, had to travel by helicopter to the Mass in central Manila's Rizal Park because roads leading there were completely blocked by people.


People perched atop vehicles, traffic lights and anywhere that looked like offering a vantage point to catch a glimpse of the leader of the world's some 900 million Catholics.


They began to disperse, however, as the word spread that the Pope was not going to travel the three kilometers from the apostolic nunciature to the park by road in his bulletproof Popemobile but that instead he had traveled by air.


The huge mass of people remained undiminished inside the park, where thousands had begun gathering Saturday and in its immediate vicinity. "I have personally never seen crowds this big in my life," Vatican official Archbishop John Foley said.


Vehicles carrying people trying to reach the Mass had to stop well short of Rizal Park.


Philippine television showed a group of bishops inching their way through the crowd in single file, hanging on to each other to make sure they did not get separated.


In a homily at the Mass, the Pope said millions of young people the world over were falling into "subtle but real forms of moral slavery".


"They abuse the beautiful gift of sexuality, they abuse drink and drugs, thinking that such behavior is all right because certain sectors of society tolerate it."


He called on young Christians to live as an example to their peers, and said their first challenge began right at home where parents and children are often at loggerheads.


In Port Moresby, despite the limits on numbers who could enter the tiny church where the pope held mass, his visit here to honor Peter ToRot, a native killed by the island's Japanese occupiers at the end of World War II was still "nambawan samting tru," pidgin English for "a big deal."


Thousands lined a 14 kilometer-long motorcade route to see John Paul seated under a yellow canopy in the back of an improvised Popemobile.


Philippine security officials Monday confirmed a plot to kill the Pope during his visit to Manila but released few details.


"It was a threat on the life of the pope. That's all I can say," said Brigadier General Leo Alves, chief of the Presidential Security Group, which organized security during the pontiff's visit.


Rumors swept Port Moresby late Monday that police forces had launched a massive search for possible assassins.


Police admitted they were seeking two Iranians traveling on business visas, saying they want to make "an additional security clearance." The men checked out of their hotel three hours before the Pope arrived.


John Paul stays until Wednesday, then moves on to Australia and Sri Lanka. (Reuters, AP)