VATICAN CITY (AP) - Biker culture has come to the Vatican.

Pope Francis on Sunday blessed thousands of Harley Davidsons and their riders as the American motorcycle manufacturer celebrated its 110th anniversary with a loud parade and plenty of leather.

Thundering Harley engines nearly drowned out the recitation of the Our Father prayer in Latin that accompanied the Pope as he greeted the crowd before Mass.

In St Peter's Square, bikers in their trademark leather Harley vests sat alongside nuns and tens of thousands of faithful Catholics taking part in an unrelated, two-day pro-life rally, the centerpiece of which was Pope Francis' Mass.

The Pope addressed them both after Mass, giving a blessing to the "numerous participants" of the Harley rally.

Tens of thousands of Harley owners from around the world descended on Rome for the anniversary.