On Tuesday a priest had his throat slashed by two Islamic State terrorists at his church in France.
The Metropolitan Police said it had circulated specific advice on how churches can protect themselves.
Neil Basu, Deputy Assistant Commissioner, said: "Following recent events in France, we are reiterating our protective security advice to Christian places of worship and have circulated specific advice today.
"We are also taking this opportunity to remind them to review their security arrangements as a precaution."
Professor Anthony Glees is the Director of the Centre for Security and Intelligence Studies at the University of Buckingham.
On Premier's News Hour he said church wardens should be "particularly bright eyed at the moment" and is encouraging them to look out for suspicious activity and people you wouldn't expect to come to a church.
He said: "People should be alert, people shouldn't be hysterical.
"Above all they should remember that the advice they are always given is, if there is a problem you should run away from it."
The Islamic State terror group has claimed responsibility for the killing, describing the two knifemen who slit the throat of 85-year-old Father Jacques Hamel and seriously injured an 86-year-old parishioner as its "soldiers".
French President Francois Hollande called Pope Francis on Tuesday night and promised to protect churches in France.
"To attack a church, to kill a priest, is to profane the Republic," said the politician.
Elsewhere Prime Minister Theresa May has vowed that Islamist terrorists "will not prevail".
Speaking during a visit to Italy, Mrs May called on European states to step up intelligence-sharing, which she said was "one of the best ways in which we can work together to ensure that we deal with this threat, to protect our citizens, but also to ensure that the terrorists do not win".
And she added: "They are trying to attack our values. They are attacking our way of life. They will not prevail."
Earlier this week the Home Secretary Amber Rudd made a prearranged announcement of new measures to combat hate crime, including a £2.4 million fund to pay for extra security at places of worship.
