A YouTube star has prompted alarm among her fans after posting a bizarre video which many feared contained a secret plea for help.

London-based fashion vlogger Marina Joyce, who has over 600,000 subscribers, stirred concern after posting a clip titled “Date Outfit Ideas” in which she appeared to be disorientated and ill at ease.

Fans claimed they could hear the message “help me” whispered and speculated she was being held against her own will. Joyce also appeared to have bruises on the backs of her arms in the clip.

Police moved to allay mounting fears over the 19-year-old's well-being, saying officers had visited her and she was "safe and well".

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After Joyce released her video, she asked her followers to meet her in east London at 6.30am on 3 August for a party. This sparked further concern with fans warning people not to attend and saying the police should go instead.

As fans speculated over Joyce's welfare, a number have theories emerged, with the hashtag #SaveMarinaJoyce trending on Twitter. While some suggested she may have been the victim of some form of hostage situation others posted theories speculating on her state of mind.

Joyce is now assuring fans that she is well and they do not need to worry.

“I'm TOTALLY fine guys, I am feeling very good today and it's actually so heartwarming to see so many people care about me,” she said on Wednesday.

She has also promised to speak to fans via a Livestream.