The woman, named by as Meredith MCLarty, has been harassing the British actor since 2014, and police are investigating after she wrote on social media that she planned to kill Monaghan.

She posted on Twitter back in March 2015 that she planned to assassinate Monaghan just like Mark Chapman shot dead John Lennon in New York in 1980: "Three words ...Mark David Chapman..." She went on, "Save #domswildthings (Monaghan's Twitter handle)."

The threat has only come to light after legal documents on the case became public on Friday (25Mar16).

A restraining order against MCLarty was put in place last year (2015), after Monaghan claimed her behaviour was not that of a fan, but of an obsessed stalker. He said in legal documents that MCLarty claimed she had been in love with him since 2001, and was bombarding him with delusional emails and tweets.

"Don't make me have to hurt you!" is one of the messages she is reported to have sent to him.

She was later arrested for violating the order by continuing to harass the actor online, and is now on the run. There is a warrant out for her arrest, TMZ reports.

Monaghan starred as Meriadoc 'Merry' Brandybuck in Peter Jackson's epic fantasy trilogy The Lord of the Rings opposite Elijah Wood, Ian MCKellen and Orlando Bloom. He is also known to fans as Charlie Pace on J.J. Abrams' TV show Lost.