Leaflets calling for Muslims to be punished, butchered and killed on a particular day were sent to people in six different communities in United Kingdom over the weekend.
The letter bears an image similar to the royal coat of arms and there is also an image of a dagger with the letters MS, suggesting it is linked to so-called Muslim Slayer who targeted mosques in London and the United States previous year with similar threats.
According to BBC, letters with images of A4 notes, containing a list of violent acts alongside a number of points for performing them, are said to be widely shared in various parts of Britain.
UK Police have released a hate crime investigation after people received letters asking them to carry out attacks on Muslims.
West Yorkshire Police came out with an official statement.
The organisation said it had received reports of the letters being sent to addresses in London, Yorkshire and the Midlands.
"We urge anyone who has received this letter to report to us in confidence or to ring the non-emergency 101 number", it said on its website.
One letter was sent to the business address of Liberal Democrat councillor Riaz Ahmed in Bradford.
"Punish a Muslim Day" - we continue to receive reports of letters received from across the country.
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A police spokesman said: "Counter Terrorism Policing North East are coordinating the investigation at this time and will consider any potential links to existing enquiries".
"It is essential that all letters and envelopes are kept and handled minimally to preserve evidence for the police to investigate", the monitor said, advising recipients.
He added: 'It was not addressed to anyone, just the address and postcode as if it was sent out randomly.
"If any constituent has received a letter, or is concerned, contact me at firstname.lastname@example.org or if you'd rather, contact @TellMamaUK".
Even though counter-terror police found no connection between this letter and the one sent to a mosque in Manchester last November, this incident should not be taken any lightly.
A Metropolitan Police spokesperson said that the letter is being investigated: 'The MPS does not tolerate any form of hate crime.
'It has a second class stamp on the plain white envelope and the frank mark is Sheffield. It was posted yesterday.
"They are inciting violence against the Muslim community", she said.
Police forces across the country are continuing to investigate and are were working with anti-racism groups like Tell Mama UK.
Police in Bradford have acknowledged they are investigating reports of the letters. "You know, it's what we do". It said the letter had "clearly originated from a disaffected section of society" but had to be treated seriously "as it may very well get into the hands of other like-minded people who are looking for a prompt to act".