Bedfordshire Police were called to the Masjid-e-Ali mosque in Beechwood Road, Luton, on Tuesday night following reports of a self-flagellation ceremony.
Members of the public contacted the police because they were concerned about the ceremony.
Self-flagellation is the act of hitting yourself with a whip as part of a religious ritual.
A member of the public saw officers at the mosque, he said: “I am very concerned, there has been a lot of police at the mosque since Tuesday night.
“Men have been turning up with knives for this self-flagellation and they have been there all day today (Wednesday). Children should not have to see that.”
A spokesperson for Bedfordshire Police said: “We had received concerns from members of the public regarding a self-flagellation ceremony due to take place on Ashura Day (11/12th October).
“We recognise and understand that this is an important and highly spiritual day for many.
“However, calls were made to our Force Control Room last night (Tuesday) reporting concerns about the activity and officers attended the Masjid-e-Ali mosque to provide visible reassurance and help prevent any possible disorder.
“No arrests were made. The force Community Cohesion team continues to work closely with the mosque committee and with partners including Luton Borough Council, and will be providing a policing presence at further events scheduled in Luton throughout the week.”
Luton Borough Council is working with Bedfordshire Police to monitor the situation, a spokesperson for the council said: “Police and council officials were called to Masjid-e-Ali Mosque last night due to fears that children were present at an event which included self-flagellation.
“The Council had previously expressed its deep concern to Mosque leaders about the negative impact and distress that would be experienced by children placed in a situation where they witnessed or participated in any self-flagellation events involving weapons and the spilling of blood.
“On arrival, officers were informed that the self-flagellation had already taken place in a separate room where no children had been present.
“Officers supported the Mosque leaders in encouraging attendees to leave the event in a calm, respectful manner.
“The Council continues to work alongside the police and the community to actively monitor reaction to last night’s events and will respond to any reports that suggest the safety of children may have been put at risk.”