The Metropolitan Police has written to faith leaders across London asking them to respect lockdown regulations.
The letter was sent last week by Commander Catherine Roper, from the Met's crime prevention unit, amid rising numbers of Covid-19 in the capital, and ahead of major religious festivals including Diwali, Hanukkah and Christmas.
Commander Roper thanked faith leaders who had adhered to the restrictions but said it was "deeply regrettable" that "small pockets" in the religious community had insisted on breaching rules.
"London's Faith Sector have showed enormous strength, compassion and hope to communities across London who have been deeply affected by the Coronavirus pandemic," she said.
"Without them, many Londoners would have felt alone and vulnerable. I would also like to thank them for the support they have shown officers in an effort to keep our communities safe and prevent further spread of Covid-19.
"London is at a critical point in fighting this virus and it is right that we all continue to take the right steps to look after each other, and comply with the Government regulations.
"We know that the overwhelming majority of Faith communities in London have made incredible sacrifices and found new ways, such as online meetings, to continue services and keep their patrons safe.
"Upsettingly however, there have been small pockets where religious venues have breached the regulations, potentially putting people in danger of spreading the virus. This is deeply regrettable and, in the interests of public safety, we have attended those incidents and ensured that crowds are dispersed."
Places of worship have been forced to close during England's second national lockdown, with the exception of individual prayer, funerals, broadcasting services, and running essential services like food banks and formal daycare.
The Met's plea was issued days before a baptism service in London over the weekend made headlines after it was broken up by police.
The letter concludes by appealing to faith leaders to keep lockdown rules.
"As our city continues our collective fight against the virus, I would urge places of worship and Faith communities across London to observe the current restrictions, which includes faith venues being available for 'independent prayer' only," she wrote.
"This is prayer that is not congregational or communal and so these cannot be led by a religious leader. However there must be a risk assessment in place to show how this can be managed safely."