United States President Donald Trump has accused New York state officials of trying to "take down" the National Rifle Association as the powerful gun rights group faces internal divisions and allegations of financial improprieties.
New York's attorney general, Letitia James, has issued subpoenas as part of an investigation related to the NRA, but she declined to elaborate.
The New York Times reported the probe relates to the group's tax-exempt status.
"The NRA is under siege by (New York Governor 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. It must get its act together quickly, stop the internal fighting, & get back to GREATNESS - FAST!" Trump said in a Twitter post.
The gun group was roiled over the weekend when internal disputes spilled into the open at its annual meeting in Indianapolis, when retired US Marine Lieutenant Colonel Oliver North said he will step down as NRA president.
North said he was being forced out because of his allegations that NRA leaders engaged in financial improprieties.
The NRA board went into executive session during a meeting on Monday as it debated next steps, according to reports.
The NRA, with more than five million members, is the most powerful and well-connected gun lobby in the US.
Trump has embraced the gun lobby, vowing not to tighten US firearms laws and advocating proposals such as arming teachers as a way of preventing school shootings.
On Friday, he used the NRA annual meeting in Indianapolis to announce he was pulling the US out of an international arms treaty signed in 2013 by Democratic President Barack Obama but opposed by the NRA and conservative groups.
The NRA spent $US30.3 million to support Trump's 2016 presidential campaign, according to the Centre for Responsive Politics, a group that tracks campaign spending.