VATICAN CITY (AFP) - Pope Francis condemned as "slave labour" on Wednesday the work conditions endured by victims of a factory collapse in Bangladesh in which more than 400 people have been found dead,.

"A headline that really struck me on the day of the tragedy in Bangladesh was 'Living on 38 euros (S$61) a month'. That is what the people who died were being paid. This is called slave labour," the Pope was quoted by Vatican radio as saying during a homily.

At a separate venue, Francis urged political leaders to make every effort to create jobs, saying unemployment was caused by economic thinking "outside the bounds of social justice".

"I call on politicians to make every effort to relaunch the labour market," the Argentine Pope told thousands of followers at his weekly general audience at St Peter's Square, which coincides with May Day demonstrations around the world.

"Work is fundamental for dignity," he said. "I think of labour market difficulties in various countries. I think of people, not just young people, who are unemployed often because of an economic conception of society based on selfish profit outside the bounds of social justice."

As the former archbishop of Buenos Aires, Cardinal Jorge Bergoglio, Francis became a leading voice on the side of the dispossessed during his country's devastating economic crisis. The nation suffered recessions in 2008 to 2009, as well as in 2011.