The pictures of the Beauty And The Beast star show her trying on outfits during a fitting.
But her spokesman, who could give no details on who stole the images, made it clear they did not show the actress nude – contrary to rumours circling online that she might have been the subject of a nude photo leak.
He said on Wednesday: “Photos from a clothes fitting Emma had with a stylist a couple of years ago have been stolen.
Many users of Twitter and Reddit have said there are pictures of the actress on the “dark web” – an encrypted network that allows users to exchange often illegal information and services without identifying themselves.
Others have said the photographs are on 4Chan, a message board in which the anonymous posts delete themselves shortly after being submitted.
The alleged hack came to the attention of social media late on Tuesday night, with many tweeting that they had seen the pictures.
Posters on a Reddit thread about the reported hack have claimed to have seen the pictures, as well as those of the actress Amanda Seyfried.
“Don’t want to break any Reddit rules so no links right now but there should be some really good drama over the next few days.”
In 2014, trolls on 4Chan posted a countdown, which seemed to threaten that they would post naked photographs of her after the time ran out.
The US website Gawker quoted posts, since deleted, that appear to show the timing of the release is no accident and that the publication of pictures would be a direct response to her speech.
One of the comments quoted said: “She makes stupid feminist speeches at UN, and now her nudes will be online.”
This threat turned out to be a hoax. Some are comparing the leak to the large celebrity photo hack which occurred in 2014.
Nude photographs of Jennifer Lawrence surfaced, as well as those purportedly showing other top Hollywood stars.
An anonymous hacker reportedly gained access to private photos on the Hunger Games actress’s mobile phone, and those of 100 others, via Apple’s online storage system iCloud.
More than 100 A-list celebrities were alleged to have been targeted, including reality TV star Kim Kardashian, singer Rihanna, models Candice Swanepoel, Cara Delevingne and Kelly Brook, and TV host Cat Deeley.
Source: Agencies and Telegraph