Pope Francis on Tuesday approved sainthood for Mother Teresa, the missionary nun who became a global if controversial symbol of compassion for her care of the sick and destitute.

The pontiff set September 4 as the date for her canonisation, elevating the Nobel peace laureate to an official icon for the Catholic faith.

The move comes 19 years after the death of the Albanian nun who dedicated much of her adult life to working with the poor in the slums of Kolkata, India.

Officials said the canonisation ceremony would take place at the Vatican -- an announcement which had been expected but nevertheless disappointed Indian Catholics who had hoped for a visit by Francis.

On Tuesday, hundreds attended a prayer meeting at Mother House in Kolkata, the global headquarters of the Missionaries of Charity where Mother Teresa is buried.

Sushmita Roy, a housewife who was one of those attending, said Teresa had long been a saint in the eyes of Indian believers.

"I came here today to pay homage to her," Roy said. "It would have been great if the canonisation of Mother Teresa would have been held in this city where she spent her life."

- 'Saint of the Gutters' -

Teresa, who was 87 when she died in 1997, was revered by Catholics and and many others around the world.

Known as the "Angel of Mercy" or "Saint of the Gutters", she won the 1979 Nobel peace prize for her work with the poor.

But she was also a controversial and divisive figure with critics branding her a religious imperialist whose fervent opposition to birth control and abortion ran contrary to the interests of the communities she claimed to serve.

Despite posthumously published letters revealing that she suffered crises of faith throughout her life, Teresa has been fast-tracked to canonisation in unusually quick time, underlining her status as a modern-day icon of Catholicism.

Teresa took the first step to sainthood in 2003 when she was beatified by Pope John Paul II following the recognition of a claim she had posthumously inspired the 1998 healing of a critically-ill Bengali tribal woman.

Last year she was credited by Vatican experts with inspiring the 2008 recovery of a Brazilian man suffering from multiple brain tumours, thus meeting the Church's standard requirement for sainthood of having been involved in two certifiable miracles.

- Gentle eye that 'sees' -
Teresa was born Agnes Gonxha Bojaxhiu to Albanian parents in 1910 in Skopje, now the capital of Macedonia.

She started her life as a nun as a teenager with a missionary order in Ireland and arrived in India in 1929. She founded her own Missionaries of Charity order in 1950 and was granted Indian citizenship a year later.

Francis, who regards Teresa as the incarnation of the kind of Church he wants to lead, met the by-then internationally famous nun three years before her death, when he was still a bishop in Argentina.

He later joked that she had seemed so formidable he "would have been scared if she had been my mother superior".

Others were much harsher in their judgement, with the likes of Australian-born feminist writer Germaine Greer and British polemicist Christopher Hitchens accusing her of contributing to the misery of the poor with what they saw as her dogmatic views.

In her Nobel acceptance speech Teresa described terminations of pregnancies as "direct murder by the mother herself".
Critics also raised questions about the Missionaries of Charity's finances and the often insalubrious conditions in the order's hospices.

The late Italian film director and writer Pier Paolo Pasolini was among those who fell under her spell, in his case when he met her during a trip to India in the early 1960s.

"She has an almost virile jaw and a gentle eye that in its gaze 'sees', he wrote, describing Teresa as a a combination of "goodness without sentimentality, someone with no expectations who is both calm and calming, powerfully practical."

India granted her a state funeral after her death and her grave has since become a pilgrimage site.