Pope Leo denounced 'unjust configurations of power, structures of sin that dig chasms between poor and rich'

Leo argued that wealth should serve 'law and justice'

The pope led Mass at the Louis II Stadium

Princess Charlene of Monaco, Prince's Albert II of Monaco and their twin children attended the mass

The highlight of the trip is to be an open-air mass at the Louis II Stadium, expected to be attended by 15,000 people.

Monaco has long-standing ties with the Holy See

Prince Albert II and Princess Charlene received the pontiff at Monaco's heliport

Though the cheers were heartfelt, the authorities had hoped for a greater turnout for the first US-born pope