VATICAN CITY (Reuters) - Pope Francis, whose criticisms of unbridled capitalism have prompted some to label him a Marxist, said in an interview published on Sunday that communists had stolen the flag of Christianity.

The 77-year-old pontiff gave an interview to Il Messaggero, Rome's local newspaper, to mark the feast of Saints Peter and Paul, a Roman holiday.

He was asked about a blog post in the Economist magazine that said he sounded like a Leninist when he criticized capitalism and called for radical economic reform.

"I can only say that the communists have stolen our flag. The flag of the poor is Christian. Poverty is at the center of the Gospel," he said, citing Biblical passages about the need to help the poor, the sick and the needy.

"Communists say that all this is communism. Sure, twenty centuries later. So when they speak, one can say to them: 'but then you are Christian'," he said, laughing.

Since his election in March 2013, Francis has often attacked the global economic system as being insensitive to the poor and not doing enough to share wealth with those who need it most.

Earlier this month, he criticized the wealth made from financial speculation as intolerable and said speculation on commodities was a scandal that compromised the poor's access to food.

(Reporting by Philip Pullella; Editing by Stephen Powell)