Pope Francis on Sunday hosted around 1,500 poor and homeless people for lunch at the Vatican, decrying indifference to poverty as the Catholic Church marked its World Day of the Poor.

"My thoughts go to those who... have promoted solidarity initiatives to give concrete hope to the most disadvantaged," Pope Francis told a mass in Saint Peter's Square ahead of the lunch.

"Recently I saw some statistics on poverty. They make you suffer - the indifference of society towards the poor," the Pope said, thanking medical staff who were providing free health care to the poor at the Vatican.

He also criticised what he called "the frenzy of running, of achieving everything right now, anyone left behind is viewed as a nuisance. And considered disposable." 

"How many elderly, unborn, disabled and poor persons are considered useless. We go our way in haste, without worrying that gaps are increasing, that the greed of a few is adding to the poverty of many others."

The Pope then joined his 1,500 guests for lunch in the Vatican's vast Paul VI Hall. 

The menu consisted of lasagna, chicken nuggets with cream of mushrooms and potatoes, dessert, fruit and coffee.

"Thank you to the Pope and thank you to the Vatican, because the Vatican helps so many poor people, and it also helps by providing medicine, this lunch of course, clothes, so many things," said Oscar, a Lithuanian who has lived in Italy for 13 years.

"We don't have good money because we work seven hours, eight hours, some people sometimes 10 hours for just €30, so this is hard," said Gambian migrant worker Lamin Jarra.

Dozens of volunteers helped bring the poor to the Vatican and serve the food, including Lorenzo Ferraro, who stressed the importance of openness towards "the most deprived, the weakest."

"In a climate of general selfishness, the Pope also remembers these people," he said.