Pope Francis has delivered an off-the-cuff, mini-encyclical on the poor, labor injustices and the environment, saying he's not preaching communism but the Gospel.

Francis' remarks to the World Meeting of Popular Movements, delivered Tuesday in his native Spanish, ran for more than six pages, single-spaced. It was one of his longest speeches yet and a clear sign that the issues are particularly close to his heart.

Francis said the poor need land, a roof over their head and work, and said he knew well that "some will think that if I talk about this, the pope is communist."

He said: "They don't understand that love for the poor is at the center of the Gospel. Demanding this isn't unusual, it's the social doctrine of the church."