Leaflets claiming critics of Islam "deserve to be assassinated" were allegedly handed out near a London mosque during a religious gathering.
Metropolitan police have launched a hate crime investigation, according to The Independent.
An imam named Syed Abdul Qadir Jilani is believed to be linked to the pamphlets, though he has denied the claims. The pamphlets, which bear Jilani's face, were handed out near the Dar-ul-Uloom Qadria Jilania mosque in Walthamstow.
Islam teaches when you live here you obey the law and the rule of law, but this is not doing that.
The booklet argues "all Muslims should support" Mumtaz Qadri, who killed former Pakistani governor Salmaan Taseer in 2011 after he supported liberal reforms to the nation's Islamic laws.
Jilani said the pamphlets were falsely attributed to him, and he does not support their message.
The mosque is also the location of the International Muslim Movement, a charity of which Jiliani is a trustee.
The pamphlets were reportedly distributed "a few months ago," according to the Evening Standard, but police were not alerted until Friday.
The Standard also reports Jilani once said on a broadcast that Muslims had a duty to kill those who insulted Muhammad.
A Scotland Yard spokesman said, "We are committed to tackling hate crime in all its forms and have long since recognised the impact of hate crime on communities."
Critics of the mosque were swift to react on Twitter.