A British-born Italian teenager who dedicated his short life to spreading the faith online and helping the poor was beatified by the Catholic Church over the weekend.

Internet and computer-mad youngster Carlo Acutis, who died of leukaemia in 2006 aged 15, was placed on the path to sainthood after the Vatican ruled he had miraculously saved another boy's life.

The beatification leaves him just one miracle away from becoming the world's first millennial saint.

The Vatican claims he interceded from heaven in 2013 to cure a Brazilian boy suffering from a rare pancreatic disease.

The beatification ceremony took place in Assisi, the home of his idol Saint Francis, who dedicated his life to the poor.

"My whole family in Argentina were very excited and asked me to pray for them, and for Carlo too. We're all very happy," said student Carla Fiezzi, who attended the ceremony.

"Young people might have been tired of a pastoral ministry that's maybe a bit out of step with the times despite all its efforts, but the Lord intervenes in history and human affairs and gives us these guiding lights," priest and Assisi Convent spokesman Enzo Fortunato said during the ceremony.

Carlo, dubbed "the cyberapostle of the Eucharist", was born in London to Italian parents, and moved to Milan with them as a young boy.

"He was considered a computer genius ... But what did he do? He didn't use these media to chat, have fun," his mother Antonia Salzano said in an interview with Vatican News.

Instead, "his zeal for the Lord" drove him to make a website on miracles, she said.

The millennial, whose body lies in state in Assisi, dressed in a tracksuit and trainers, also warned his contemporaries that the internet could be a curse as well as a blessing.

Pope Francis referred to him last year, in a warning to youngsters that social networks could foment hate.

"(Acutis) saw that many young people, wanting to be different, really end up being like everyone else, running after whatever the powerful set before them with the mechanisms of consumerism and distraction," Francis said.

"As a result, Carlo said, 'everyone is born as an original, but many people end up dying as photocopies'. Don't let that happen to you!" he said.

Carlo was religious from a young age, despite his mother saying his family had rarely attended church.

When he wasn't writing computer programmes or playing football, Carlo was known in his neighbourhood for his kindness to those living on society's margins.

"With his savings, he bought sleeping bags for homeless people and in the evening he brought them hot drinks," his mother said this week, according to the Catholic News Agency.

"He said it was better to have one less pair of shoes if it meant being able to do one more good work," she said.

He also volunteered at a soup kitchen in Milan. Assisi bishop Domenico Sorrentino said this month that a soup kitchen for the poor would be opened in his honour.

"When he died, at the funeral, the church was full of poor people. Everyone else wondered what they were doing there. Well, Carlo used to help them in secret," said Nicola Gori, who represented his beatification case.

"The family knew about it, because his mum would go with him, since he was only 15 years old. He would give them sleeping bags and food, which is why they wanted to attend the funeral," he added.

Should Carlo later be credited with the second miracle necessary for sainthood, supporters have suggested he could become the Patron Saint of the internet, although there already is one, 7th-century scholar Isidore de Seville.