The offensive letters, offering points for committing different violent acts against Muslims, were sent to a string of locations across the country this week with five police forces - West Yorkshire, South Yorkshire, Leicestershire, Nottinghamshire and the Metropolitan Police - all receiving reports.
Today Qari Asim MBE, senior Imam at Leeds Makkah Mosque, said the messages have caused alarm in the city.
“There’s no denying that these revolting letters have caused alarm amongst many in the Muslim community,” he said.
“These attempts to divide us represent the very worst of a deplorable anti-Muslim sentiment that has been rearing its head with increasing frequency over the past year.”
Mr Asim, who is also a member of the Government’s Anti-Muslim Hatred Group, said that while the letters were concerning, police across the region have taken the issue seriously.
He added: “It is reassuring, however, to see the excellent response from our authorities, and wider communities, taking this so seriously.
“It is equally important that those who have received the letters contact the police as all evidence is vital in helping them find, and hold accountable, whoever is responsible for such hateful rhetoric.”
Counter Terrorism Policing North East is leading the investigation into the messages.
Head of the unit, Detective Chief Superintendent Martin Snowden, said: "We take religious hatred extremely seriously and my officers will be carrying out a full and thorough investigation in response to these reports.
"These letters seek to cause fear and offence among our Muslim communities. They also seek to divide us. Yet in spite of this our communities have shown strength in their response to such hatred and in their support for each other.”
Assistant Chief Constable Angela Williams, of West Yorkshire Police, said public safety remains the force’s top priority.
“We understand that they may have caused concern and upset to people, especially the more vulnerable members of society,” she said.
“We are working with the communities we serve to reassure residents that, as always, everything possible is being done to ensure their safety and to catch the person or persons responsible for this.
Public safety remains our priority and I would urge our communities to be vigilant but not frightened.
“We are stronger when we stand together as one and will not be divided.”
Officers have urged anyone who believes they have been a victim of such an offence to contact their local police force on 101, or on 0800 789 321 in confidence.