Church officials will be given "in-depth" anti-terrorism training after places of worship were revealed to be "top of terrorists' hit lists".
Police will visit churches and cathedrals in London, Manchester, Liverpool, Newcastle and other cities. They will carry out Action Counters Terrorism (ACT) safety-plan training, which includes teaching survival skills and doing risk assessments for every building.
It follows the wave of suicide bombings which killed at least 250 people and wounded 500 at churches in Sri Lanka, inset.
A top police source said: "Very real intelligence has shown a number of attacks are now likely on places of worship in some of the UK's biggest cities.
"This is a very real threat and at least two attacks have already been thwarted.
"Given the recent tragedies in Sri Lanka, it is the view of the top brass that it is better to share this intelligence - not to make people fearful, but to make them prepared." They added: "Emergency plans need to be put in place, and quickly."
Police will send specialist officers to carry out training at places of worship deemed most at risk. Those at lower risk will be encouraged to complete an online training course.
The "practical" advice follows the "Run, Hide, Tell" motto, and will teach priests how to be the "lead" in getting their congregations to safety during an attack. Dep Asst Commissioner
Police will be going to carry out trainings at churches they deem to be most at risk
Dean Haydon from the Metropolitan Police said the force "stands together with communities of all faiths".
He added: "Together with our intelligence partners we continually monitor the varied threats we face, including to and around places of worship and specific communities across the country, to ensure we have the most appropriate protective security measures in place to keep people safe."
Meanwhile, insurance companies are launching terrorism policies to protect places of worship.
Our police insider added: "It is a sad sign of the times that we are having to go to these measures, but the fact is they are needed in this war against terrorism."