Italy's far-right Interior Minister Matteo Salvini has rejected calls by the African Union to retract comments he made referring to African migrants as "slaves", AFP news agency reports.

Mr Salvini said his comments had been distorted.

"In fact, in Vienna I said exactly the opposite, to defend asylum seekers and immigrants who some people in Europe use as slaves," AFP quoted him as telling journalists.

Mr Salvini's made the comments during a row with Luxembourg's Foreign Minister Jean Asselborn at a migration conference on Friday.

Mr Asselborn had suggested that Europe needed immigrants because of its ageing population when Mr Salvini, according to AFP, replied by saying: "In Italy we feel it's necessary to help our children make more children. And not to have new slaves to replace the children we're no longer having."

The AU said in a statement on Tuesday that he should "retract his derogatory statement about African migrants".

"It is the view of the African Union that name-calling will not resolve the migration challenges facing Africa and Europe," it added.