Argentina's economy ministry said on Friday it had asked the national securities watchdog to investigate whether litigation in the United States against the nation by holdouts was merely the "facade of speculative maneuver in favor of vulture funds."

The ministry said the watchdog should investigate whether the holdouts litigated simply to earn profit on defaulted bonds they bought on the cheap as well as on credit default swaps (CDS), derivatives used to insure against default.

Regarding the decision earlier on Friday by the International Swaps and Derivatives Association (ISDA) to call Argentina's missed June interest payment a "credit event", triggering payment on CDS, the ministry said it "favored some privates at the expense of others."

The Argentine securities watchdog will ask its U.S. counterpart for "precise information about the transactions of these (CDS) to investigate if the vulture funds earned a huge benefit from not reaching an agreement, either directly or via third parties".