The Rt Rev Mark Davies, the Roman Catholic Bishop of Shrewsbury, told churchgoers in Hattersley, Greater Manchester, that local communities "must stand as one" to avoid such deaths being accepted as "commonplace".
Pc Nicola Hughes, 23, and Pc Fiona Bone, 32, were attacked and killed on Tuesday as they responded to what they thought was a routine burglary call out on the Hattersley estate in Mottram.
Rev Davies led prayers for the officers, their families, friends and colleagues in a homily at morning Mass at St James the Great RC Church in Hattersley.
He said that Pc Hughes and Pc Bones were met with "merciless and ferocious violence" as they sought to protect the community.
He said: "Today, with so many across the world we remember and hold in our prayer these two police officers together with their families and loved ones and the many colleagues who deeply mourn their loss.
"We feel a sense of sorrow and outrage too. We recall how what is good in the dedicated service of the community met on our own streets with what is evil in the hate and violence which did not hesitate to indiscriminately kill.
"The sound of gunfire and a grenade exploding in the streets of this parish, the death of two young women fulfilling their duty, tragically reminds us that the police service stands as our last line of defence against the savagery of the jungle.
"If our children are not to grow up accepting the murders of Tuesday as commonplace then the police and the community must stand as one in defence of human life, overcoming whatever obstacles may prevent this trust.
"The police are there to protect us, but our protection must also be found within ourselves - in the moral values on which our homes and families are built, in the strength of our community. The commandments of God, St Augustine reminds us, were written first in our hearts before they were written on tablets of stone - they are accessible to everyone with a conscience.
"'You shall not kill' commands us in the name of God to value every human life as sacred. May these tragic events which have left everyone horrified, never allow us to lose sight of those commandments, those moral foundations on which the peace and life of our whole society is built."
Greater Manchester's Chief Constable, Sir Peter Fahy, has described how he has drawn strength after the "very, very dark day" of the murders, from his faith and belief that policing is a "calling" rather than a job.
In an interview with BBC One's Songs of Praise, Sir Peter said he has drawn strength from the "very, very dark day" when the two officers were killed by feeling that policing is a vocation rather than a job.
He said: "Greater Manchester police is a family and to have lost two colleagues this week in awful violent circumstances has just been devastating for the whole force and a very, very dark day.
"I think a lot of us feel passionately that policing is a vocation.
"It is a calling. I feel that in terms of my own faith but I know a lot of officers that don't have a faith, but feel exactly the same - that it is a vocation, that it's not just a job and I think that's almost what you go back to in difficult times and difficult circumstances that how unfair something may feel, how inadequate you may feel you do actually rely on that you're doing your best, and that this is your vocation."
Sir Peter also said he was proud to be part of an unarmed police force that uses "minimum force".
A number of remembrance services are being held today across the south Manchester area.
The Roman catholic bishop of Shrewsbury whose diocese covers the parish will be holding mass in the local church of St James the Great.
The Rt Reverend Mark Davies said: "In the face of events of such tragedy and evil of the magnitude that was visited on the streets of Mottram and Hattersley last week people turn in these moments to God.
They seek to pray and to hold in their prayers, to hold in their hearts, all those who have been involved in these events."
Yesterday, the family of a 15-year-old boy arrested on suspicion of helping Cregan said they were in "total disbelief".
The boy was detained at his school in Thameside, Manchester, on Friday by three plain-clothed officers who handcuffed him and led him away. He was held for six hours before being released on bail pending further inquiries.
Cregan, 29, was remanded in custody on Friday charged with the murders of Pcs Fiona Bone, 32, and Nicola Hughes, 23, of Greater Manchester Police, along with two further murders and four attempted murders.
The father of the arrested boy, who cannot be named, said: "My lad's never met Dale Cregan in his life. It's unbelievable.
"I understand that the police have a difficult job to do but it doesn't make any sense to me and I'm just trying to get to the bottom of how this could have happened."
Garry Shewan, Assistant Chief Constable at Greater Manchester Police, said: "This remains a complex and sensitive investigation and we continue to ask the public to search their conscience and urge anyone who has any information to contact us."
The chief constable of Wiltshire police also said that he plans to issue more officers with Taser stun guns to stop them feeling "vulnerable".
Patrick Geenty said: "Training more officers to use Tasers would do more to protect them ... I'm looking to see whether we can increase that."