Pope Francis has expressed dismay about clashes in the Democratic Republic of Congo he described as "violent and brutal."

In remarks to the faithful in St Peter's Square on Sunday, Francis singled out for concern the "many children torn from families and schools to be used as soldiers" in the fighting.

The Pope spoke days after the United Nations voiced grave concern about reports of more than 100 people killed in recent clashes between Congolese soldiers and fighters.

The vast Central African country is home to multiple militias vying for control of rich mineral deposits, and human rights groups have long expressed alarm over alleged abuses by the military in the fight against them.

Francis says he is praying for the victims as well as for religious and humanitarian personnel.