Washington (CNN) President Donald Trump on Monday accused the New York attorney general's office of illegally investigating the National Rifle Association and called on the group, which has been roiled by a leadership fight, to "get its act together quickly."

"The NRA is under siege by (New York Gov. Andrew) Cuomo and the New York State A.G., who are illegally using the State's legal apparatus to take down and destroy this very important organization, & others," Trump wrote in a tweet. "It must get its act together quickly, stop the internal fighting, & get back to GREATNESS - FAST!"

On Saturday, New York Attorney General Letitia James' office announced in a statement it had launched an investigation into the NRA and had issued subpoenas to the organization, but did not confirm what the probe was in regard to.

The investigation comes after a dispute between the group's president, Oliver North, and chief executive officer, Wayne LaPierre, in which North accused LaPierre of financial misconduct, including the improper use of $200,000 of NRA funds to purchase clothing from an NRA vendor, according to the Wall Street Journal.

It also comes nearly a year after James, during her campaign last summer, said she would investigate the NRA if elected to make sure it is complying with non-profit rules. Her campaign threat helped prompt the group to begin an internal review of its finances, which is part of what triggered the tensions between North and LaPierre.

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