Pope John Paul II will conclude one of the longest trips of his pontificate by celebrating a mass for the beatification of two Mexican Indians in Mexico City.

Many thousands of people came to Mexico City to see the Pope

The beatification of Juan Bautista and Jacinto de los Angeles, who were lynched in 1700 after denouncing the pagan activities of their communities to the Catholic authorities, is the last step before sainthood.

The Pope will preside at a prayer service in the Basilica of Our Lady of Guadalupe where on Wednesday he canonised Mexico's first indigenous saint, Juan Diego, in a ceremony watched by hundreds of thousands.

While the trip has been seen as a success, the 82-old-pontiff - who suffers from Parkinson's disease and arthritis - was visibly frail, again fuelling speculations about his health.

Jubilant crowds

During Wednesday's three-hour canonization Mass, the Pope looked extremely tired and struggled to keep his head up.

The visit has reopened debates over the existence of Juan Diego

He often stuttered while reading his homily, and at one point was apparently asked by an aid if he wanted someone else to read for him.

Juan Diego, an Indian peasant, who lived almost 500 years ago, is said to have witnessed an apparition of a dark-skinned Madonna - the Virgin of Guadalupe - who is Mexico's patron saint.

Hundreds of thousands of cheering and singing people lined the streets of Mexico City, to catch a glimpse of the Pope as he made his way to the basilica.

As the Pope was driving back from the service a teenager fired an air rifle at one of the police officers lining the route, but officials stressed the pontiff was not in the vicinity at the time.

In Mexico, the Church has lost millions of followers in recent years to Protestant evangelical groups in the largely indigenous south of Mexico, and Catholics hope Juan Diego's sainthood will halt that decline.

Traditional music

Indians dressed in plumed headdresses danced up the central aisle of the basilica as the Pope declared Juan Diego a saint.

Feathered Aztec dancers joined in the service

Three men in indigenous costumes blew conch shells and the entire congregation shook maracas.

Only 22,000 people fit into the basilica, but those lucky enough to get a ticket packed the church building and forecourt.

During the service, the Pope called upon all to respect the rights and cultures of the original inhabitants of the Americas.

Mexican waves

Mexicans have a special affection for John Paul II, who went to the country on the first foreign trip of his papacy more than two decades ago.

There was a euphoric atmosphere, which the BBC's correspondent in Mexico City, Nick Miles, said was akin to that at a pop concert.

The crowds even participated in Mexican waves as they waited for the pontiff to pass.

But the visit has reopened the debate in Mexico over the existence of Juan Diego and the Virgin of Guadalupe herself.

Non-believers say the apparition was invented by the conquering Spaniards to convert the indigenous population to Catholicism.

Mexico is the final leg of an 11-day papal tour of the Americas, that started in Canada and continued in Guadalupe.

The Pope leaves Mexico on Thursday afternoon and arrives back at the Vatican on Friday morning.