"I do not interfere in the internal affairs of Catalonia, Spain or any country, but these are international events of great importance (...). The repression appeared brutal, really brutal, because if people are peaceful and calm, leave them alone," Maduro said on state television channel VTV.
"Who is a dictator? Nicolas Maduro or Rajoy -- who has chosen blood, the club and the blow against a noble people?" he asked before comparing events to the Franco era of 1939-1975, AFP reported.
Maduro is himself accused by the Venezuelan opposition of "savage repression" during a wave of protests between April and July, which left some 125 people dead.
But he justified police and military action in his country by arguing Catalonians "did not have hoods or homemade guns like the Venezuelan right."
Relations between Caracas and Madrid deteriorated following the creation of an all-powerful Constitutional Assembly in Venezuela -- with Spain pressing the European Union to impose sanctions on Maduro's government.
Hundreds were injured in clashes during the Catalan referendum Sunday.