UK churches insist they remain "open to all" despite the murder of a French Catholic priest while celebrating mass on Tuesday.
Father Jacques Hamel had his throat cut by two men who entered his small church in Saint-Etienne-du-Rouvray. The attackers held the five members of the congregation hostage before being shot dead by police. One other person was seriously wounded in the incident.
ISIS has since claimed responsibility and the French President, Francois Hollande, said the country was "at war".
But British churches remained defiant in the wake of possible "copycat attacks" in the UK.
A spokesman for Cardinal Vincent Nichols, the head of the Catholic Church in England and Wales, said "of course" churches would remain open. "Everyone is welcome," he told Christian Today. He added the Church would follow any security advice issued by the police but would not be adding any security procedures of their own.
A spokesman for the Church of England said that despite the threat Church buildings would remain "open to all".
He said in a statement: "Where there are known risks, churches take measures to ensure the safety and security of worshippers and visitors."
A new £2.4m fund for security measures in places of worship was made available on Tuesday in a pre-planned announcement by the Home Secretary. The CofE welcomed the move and added: "All public ministry involves being vulnerable to others, so security measures are good sense in uncertain times."
Churches can apply to the fund for security equipment such as CCTV, bollards and gates but not security personnel.
Police urged British churches to review their security after the attack near Rouen, northern France. Neil Basu, the Metropolitan police's deputy assistant commissioner, said there was no specific threat to UK Christians but told believers to be "alert".
Using the Arabic acronym for Islamic State, he said: "As we have seen, Daesh and other terrorist groups have targeted Christian as well as Jewish and other faith groups in the west and beyond. 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."
He added: "While the threat from terrorism remains unchanged at severe, we urge the public to be vigilant. Be alert and not alarmed and report any suspicious activity. The UK police service is working tirelessly with our partners to confront the threat and protect all our communities."
In specific advice sent to churches, it is believed police have suggested churches review when public can enter the buildings and when they should be locked.
Meanwhile in France leaders from different faiths called for more security at their places of worship after a meeting with President Hollande on Tuesday night.
Muslim leader Dalil Boubakeur, rector of Paris's Grand Mosque, expressed "profound sorrow" after the attack which he described as a "blasphemous sacrilege".
He said religious leaders "deeply desire that our places of worship are the subject of greater [security] focus, a sustained focus", as even "the most humble place of worship" can be targeted.
The Archbishop of Paris, Andre Vingt-Trois, praised the good relations between France's religions.
"We must not let ourselves get pulled in to Daesh's political games," he said and added the group wanted "to set children of the same family against each other".
Release International, a Christian persecution charity, said the attack was a "wake up call" for churches in the UK and urged churchgoers to "refuse fear and to value, cherish and celebrate the freedom we have".
Chief executive Paul Robinson said: "The terrorists' intention is to stir up hatred and division and to rob us of our freedom. But what Release has seen around the world time and again is something much more powerful than hate. We have seen the words of Jesus lived out in the lives of ordinary Christians – love your enemies.
"The message of persecuted Christians around the world is to refuse to hold hatred in your heart. Forgive, love and continue to walk in freedom. Love kills hate."
