CAGLIARI – Pope Francis made one of his strongest attacks on the global economic system on Sunday, saying it could no longer be based on a "god called money" and urged the unemployed to fight for work.

Francis, at the start of a day-long trip to the island's capital, put aside his prepared text at a meeting with unemployed workers, including miners in hard hats who told him of their situation, and improvised for nearly 20 minutes.

"I find suffering here ... It weakens you and robs you of hope," he said, "Excuse me if I use strong words, but where there is no work there is no dignity."

The crowd of tens of thousands of people in a square near the city port chanted "work, work, work" at the gathering, which took on the feel of a union rally.

Cagliari has a youth unemployment rate of about 51 percent and much of the island's mining and industrial sectors are in crisis, with many unemployed.

But the pope made clear that his assessment was not limited to the local.

"It is not a problem of Italy and Europe ... It is the consequence of a world choice, of an economic system that brings about this tragedy, an economic system that has at its centre an idol which is called money," he said to the cheers of the crowd.

"We don't want this globalised economic system which does us so much harm. Men and women have to be at the centre (of an economic system) as God wants, not money," he said.

While Francis's predecessor Benedict also called for changes to economic systems, he was more likely to use dense intellectual language.

Francis, who as bishop of Buenos Aires sided with unemployed workers in their conflict with government austerity plans, ended his improvised speech with a prayer asking God to "give us work and teach us to fight for work".

Francis said he did not want the crowd to see him as a "cordial manager of the Church who comes here and says to you 'have courage'".

He added: "I don't want this. I want this courage to come from inside me and push me to do everything I can as a pastor and a man."