The rapper - who shot to international fame with 'Gangnam Style' earlier this year - apparently performed at an anti-US concert back in 2004 and urged the crowd to "kill those f**king Yankees".
The performer - real name Park Jae-sang - was pictured smashing a model US military tank back in 2002 at a concert which was in opposition to 37,000 troops stationed on the Korean Peninsula, reveals The Hollywood Reporter.
Two years later in 2004, Psy performed at a protest concert after a South Korean missionary was executed in Iraq, as a revenge killing for the country's support of the Iraq war spear-headed by the US.
"Kill those f**king Yankees who have been torturing Iraqi captives /Kill those f**king Yankees who ordered them to torture /Kill their daughters, mothers, daughters-in-law and fathers /Kill them all slowly and painfully," he reportedly rapped.
Certain parts of the American media have now asked why Psy wasn't questioned about his purported anti-American past when interviewed on The Ellen DeGeneres Show and The Today Show earlier this year.
Watch the music video for Psy's 'Gangnam Style' below: