The heart of a revered 19th century Argentine friar and patriot was stolen from an urn in the Franciscan monastery where it was kept for years as a religious relic, a church official said.

Whoever scooped up friar Mamerto Esquiu's heart on Tuesday left the urn it was stored in behind, said Jorge Martinez, head of the San Francisco monastery in the northwestern province of Catamarca.

"The theft was carried out because of the heart -- nothing else was stolen," he told local reporters. "It's very sad."