Hackers have launched a new spam campaign claiming to come from a professional assassin in an attempt to steal money, security experts warn.

Users receive an email which states that the assassin is stalking them. However, the message claims the killer will drop the contract if they pay them £40,000. Upon receiving an initial payment of £10,000 the assassin asserts that he will produce taped evidence of the contract to murder the email recipient.

The message includes the subject line "read this to be safe" and threatens the user not to contact the police or forward the message to the authorities, security professionals claim.

"This is surely one of the sickest phishes yet seen - the intention of this email is quite clearly to frighten the recipient into coughing up a substantial amount of money or, at the very least, their bank account details," said Graham Cluley, senior technology consultant for Sophos.

"Innocent, vulnerable people could be scared into believing that the contents of the email are truthful, while the not-so-innocent are arguably even more likely to be hoodwinked. It may be hugely unnerving to receive such threats, but the only way to stop the distribution of these messages is for users to stop responding," he added.