The Islamic State continues to claim responsibility for Sunday's deadly mass shooting in Las Vegas, reportedly on Thursday specifying its claim that the gunman had converted to Islam before his rampage.

The militant group, also known as ISIS, claimed in its weekly newsletter that the shooter "converted to Islam six months ago," according to a translation from the SITE Intelligence Group. The group initially said on Monday that the gunman had converted to Islam "several months ago."

As was the case on Monday, ISIS did not provide evidence for its claim, and authorities in the US have said they have found no connections between the shooter, Stephen Paddock, and international terror groups.

Thursday's newsletter referred to the gunman as "Abu Abdul Barr al-Amriki" and included an image of the Mandalay Bay Resort and Casino, the hotel from which Paddock fired on 22,000 concertgoers below, drenched in blood.

Despite the Islamic State's absence of evidence to support its claim, the New York Times correspondent Rukmini Callimachi‏ argued in a series of tweets on Thursday that it shouldn't necessarily be discounted outright.

ISIS generally does not claim responsibility for attacks it did not authorize or inspire, Callimachi wrote — she said she could find only three instances since 2014 in which the group did so.

"No proof is provided, but ISIS has rarely claimed attacks that were not by either their members or sympathizers," Callimachi said, later adding: "Yes, the group frequently exaggerates death tolls & yes, they inflate & distort details, but the crux of the claim is typically correct."