Pope Francis has recognised a second miracle attributed to the late Mother Teresa, clearing the path for the nun to be elevated to sainthood next year, the Vatican said Friday.

Mother Teresa, celebrated for her work with the poor in the Indian city of Kolkata, is expected to be canonised as part of the pope's Jubilee year of mercy.

In the Vatican's Jubilee calendar, September 4 is already marked as a day dedicated to the late nun's memory and her canonisation is likely to take place then, experts say.

Archbishop of Kolkata Thomas D'Souza said the Vatican has recognised that Mother Teresa cured a Brazilian man suffering from multiple brain tumours in 2008.

Teresa, who was born to Albanian parents in what is now Skopje in Macedonia, was known across the world for her charity work. She died in 1997 at the age of 87.

- 'Saint of the Gutters' -

Nicknamed the "Saint of the Gutters", she dedicated her life to the poor, the sick and the dying in the slums of Kolkata, one of India's biggest cities, founding the Missionaries of Charity order of nuns. She won a Nobel Peace Prize in 1979.

She was beatified by then pope John Paul II in a fast-tracked process in 2003, in a ceremony attended by some 300,000 pilgrims. Beatification is a first step towards sainthood.

Her missionary order in Kolkata -- formerly known as Calcutta -- said it was "thrilled" and grateful to Pope Francis.

The pontiff met the late nun in Rome in 1994 when he was a bishop, and joked last year that while he admired her strength, he "would have been scared if she had been my mother superior".

Sunita Kumar, a missionary spokeswoman who worked closely with Mother Teresa, said the late nun was an extraordinary woman who believed hard work was the best way to serve God.

"She of course read the Bible but her main understanding was to serve the poor," Kumar told the NDTV network. "Look at the work she did, not a day's holiday, not a day's rest."

In 2002, the Vatican officially recognised a miracle Mother Teresa was said to have carried out after her death, namely the 1998 healing of a Bengali tribal woman, Monika Besra, who was suffering from an abdominal tumour.

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The traditional canonisation procedure requires at least two miracles.

The second miracle involved a 35-year-old Brazilian man who had not long been married when he was diagnosed with eight brain tumours in 2008, according to Vatican expert Andrea Tornielli.

- Tumours 'disappeared' -

On December 9, the man was wheeled into the operating room in an induced coma, but doctors were forced to delay the medical procedure by half an hour because of technical problems.

While they waited, the man's wife led prayers to Mother Teresa in the hospital's chapel. When the surgeon returned to the operating room he is said to have found the patient awake, sitting up and asking "what am I doing here?"

"I have never seen a case like it," the surgeon was quoted as saying, after a CAT scan showed that the Brazilian's tumours "had suddenly and inexplicably disappeared", Tornielli said in La Stampa daily.

For all the reverence with which her name and memory are treated, Mother Teresa was not without her critics.

She has been accused of trying to foist Catholicism on the vulnerable, with Australian feminist and academic Germaine Greer calling her a "religious imperialist".

One of her most vocal detractors was the British-born author Christopher Hitchens, who accused her of contributing to the misery of the poor with her strident opposition to contraception and abortion.

Questions have also been raised over the Missionaries of Charity's finances, as well as conditions in the order's hospices where there has been resistance to introducing modern hygiene methods.

A series of her letters published in 2007 also caused some consternation among admirers as it became clear that she had suffered crises of faith for most of her life.

She was granted Indian citizenship in 1951 and received a state funeral after her death.

Her grave in the order's headquarters has since become a pilgrimage site.