Her order, the Missionaries of Charity, said 8,000 people attended memorial masses around Calcutta, and many visited Mother Teresa's grave.

Mother Teresa won the Nobel Peace prize in 1979

In Rome, the Pope described her as a "gift from God to the poorest of the poor".

He appealed to world leaders to disarm and divert defence budgets to help the poor.

"Her memory is alive in each one of us, in the entire church and the entire world," the Pope said in St Peter's Square at the Vatican.

At a special early morning mass at Mother House, the headquarters of Mother Teresa's charity, in Calcutta, India, priests from different churches joined nuns from the order she founded in 1948, the Missionaries of Charity, to hold prayers.

Jane Little: "To many Mother Teresa is already a saint"

Catholic Father Francis Gomez, who led the mass, said Mother Teresa's "loveable memory, which guided us to the path of God, is still fresh in our hearts."

Father Gomez also said he awaited "the day of beatification and sainthood" of Mother Teresa, reflecting the views of many Catholics.

Thousands pay respects

Thousands of visitors queued at the graveside of Mother Teresa to pay their respects.

Sister Nirmala, successor to Mother Teresa praying before her tomb

One of them, a 50-year-old disabled man, whose treatment Mother Teresa funded over the years, said "in her death last year, I lost my mother again."

In the order's main chapel, a statue of Mother Theresa, legs folded by her side, was placed at the spot where she would normally sit to attend services.

Hourly prayers have been scheduled at the headquarters of the Missionaries of Charity throughout Saturday.

Calls for beatification

In recent months many Catholics have urged the Pope to declare Mother Teresa a saint.

The Vatican has sent a special observer to India to record reports of miracles associated with her.

But the BBC religious affairs reporter says a Vatican spokesman recently denied rumours that the Pope intends to speed up the canonisation process which usually takes many years.

A life with the poor

The mission will have 614 centers across the world by the end of the year

Mother Teresa, an Albanian born in the capital of the former Yugoslav republic of Macedonia, Skopje, won the Nobel Peace prize in 1979, for her work for the poor and downtrodden in Calcutta.

Mike Wooldridge on past and current controversies surrounding Mother Teresa's Missionaries of Charity

In 1980, 70 years after her birth, Mother Teresa returned to Skopje to inaugurate a mission of her Missionaries of Charity and was made a citizen of honour by city officials.

She died at the age of 87, in Calcutta on 5 September 1997, following a heart attack.