An online threat to release nude photos of British actress Emma Watson after she launched a gender equality campaign at the United Nations was revealed on Wednesday to be a hoax - and probably by a hoax group.

Until late Tuesday night, the EmmaYouAreNext.com website, which appeared earlier on online message board 4chan, showed a countdown clock and a threat to release illegally obtained photos of the Harry Potter actress.

Earlier this month personal photos of actress Jennifer Lawrence and Sports Illustrated swimsuit model Kate Upton were posted on the image-sharing forum 4Chan.

But the threat emerged to be a hoax, with the EmmaYouAreNext website redirecting to the web page of Rantic (www.rantic.com), an online domain that claims to be a social media marketing enterprise, that featured the message #shutdown4chan.

"Join us as we shutdown 4chan and prevent more private pictures from being leaked," said a statement on the sparce Rantic website, adding the company had been hired by celebrity publicists to bring this issue to attention.

However, Rantic itself could be a hoax, according to various media reports. No media outlets were able to track down the company directly and emails sent by the Thomson Reuters Foundation bounced back.

The incident happened after Watson, a United Nations Women's Goodwill Ambassador, gave a speech in New York on Saturday amid a blaze of publicity, urging men to join the fight for gender equality and end violence and discrimination against women.

Her speech marked the launch of "HeForShe" campaign that aims to mobilize 1 billion men and boys over the course of 12 months to support gender equality. By late Wednesday the number signed up to pledge to fight for equality had reached 100,000.