Facebook users have been issued a warning over a scam in Facebook Messenger which has cost one unfortunate user more than £400,000.

Experts have warned the ‘deepfake’ scam could catch anybody out as users are urged to remain vigilant.

The scam sees people lose out on money thinking they are talking to celebrities with one user losing out on $500,000 after thinking the were talking to Marvel star Mark Ruffalo, who plays The Incredible Hulk in the franchise.

Japanese artist Chikae Ide shared the warning with Japanese newspaper The Asahi Shimbun. She warned how she was convinced she was talking to the real person over webcam due to the technology used.

Ide said: “I’m sure it was Mark himself who was behind the screen chatting with me.

"He respected my work, and he said that I, this old lady, am beautiful. He also said the age difference is no problem for him, and he wants to make me happy."

The fraudster posing as the Hollywood star told Ide “I will never make you sad,” as the pair talked non-stop.

Ide sold personal belongings and delayed paying her staff to keep funding who she believed was Mark Ruffalo.

She even dipped into her son’s savings to keep funding the fraudster.

"It was such a stupid experience," she said: "But I hope people take it as a lesson. I apologize to my friends and acquaintances who lent money to me while I refused to listen to them.

"I swear I will continue to draw manga until I die to pay them back."