The dissident republican group that murdered journalist Lyra McKee has been urged to walk away from violence.
Father Martin Magill was addressing the funeral service of Ms McKee at St Anne's Cathedral in Belfast.
The 29-year-old was murdered by the self-styled 'New IRA' in Derry last Thursday night after a gunman opened fire on a street full of people during disorder in the Creggan area.
Fellow journalists formed a guard of honour as the service for their murdered colleague began. Applause rang out around St Anne's Cathedral as the coffin was carried in.
The congregation was led by Ms McKee's partner Sara Canning, her mother Joan, brothers Gary and David and sisters Joan, Nichola and Mary.
"I plead with you to take the road of non-violence to achieve your political ends," Fr Magill told a congregation.
"It was encouraging to see that those who provide a political analysis to the organisation responsible for her death chose to call off their parade on Easter Monday following the call from Father Joe Gormley, the parish priest in Creggan where Lyra was killed.
"To those still intent on violence, I ask you to listen to the majority of the people on your beloved island of Ireland who are calling on you to stop."
In introductory comments, Dean Stephen Forde said: "Lyra was a person who broke down barriers and reached across boundaries.
"This was her hallmark in life, this is her legacy in death."
He said she was a child of the 1998 Good Friday Agreement, which largely ended decades of violence and talked of the hopes for an end to the prejudices of the past and the possibilities of a new future.
President Michael D Higgins, Taoiseach Leo Varadkar and British Prime Minister Theresa May were among those who attended.
Tánaiste and Minister for Foreign Affairs Simon Coveney, Minister for Children and Youth Affairs Katherine Zappone, Northern Ireland Secretary Karen Bradley and British Labour leader Jeremy Corbyn were also at the service.
Fr Magill said he "dares to hope" that the tragedy can be "the doorway to a new beginning".
He paid tribute to those who had left red hand prints on the offices of the dissident republican political group Saoradh at the weekend, describing it as a "powerful gesture of non-violence", and also commended those who have given information about the murder to police.
"There is a rule in many of our communities that we do not, we should not, give information to police, and that to do so is to become a 'tout'," he said.
"But that was one of a number of rules - rules that also said that it was OK to brutalise children for petty crimes, or rules that say you can live in the locality until you are told you can't, or rules that said the only way we could gain 'freedom' was by other fellow human beings losing their lives.
"But this week I have seen these rules turned on their head. I have seen many people stand up and condemn this culture of violence and coercive control.
"We need to send a very different message and so I appeal to those who have information about Lyra's murder but who haven't yet come forward to do so now.
"If you want to see an end to these brutal rules, and see a new society built on justice and fairness, on hope and not fear, then you can help build that society by letting the police know what you know.
"There will be special measures put in place to ensure your safety and where you will not be intimidated by coercive controllers, if you do so."
Fr Magill also urged Northern Ireland's politicians to start talking to reform the power-sharing government, which has been collapsed for more than two years.
"Many, many wonderful things have been said about her including the warm and deserved tributes paid to her by the Secretary of State and by MPs of all parties in the House of Commons yesterday evening," he said.
"In death Lyra has united people of many different backgrounds as further evidenced by this diverse congregation at her funeral."
The Belfast priest said he had met Ms McKee several times and told the funeral of her upbringing in the north of the city, attending Holy Family Primary School and St Gemma's High School, where her love of Roald Dahl novels helped her overcome early struggles with reading, and her later love of the Harry Potter books by JK Rowling.
Fr Magill recalled in recent years speaking with her as she researched her book The Lost Boys, about youngsters who had disappeared in the past, describing her as "like a dog with a bone" about the project.
"I certainly experienced her gentle, determined doggedness," he said.
"I pray her work will be taken up and that their bodies will be found and, even more importantly, that there will be no more lost boys or lost girls.
"When I consider Lyra's determination, it strikes me that she was the embodiment of the St Gemma's school motto: truth and charity."
Those attending the funeral were asked to wear Harry Potter and Marvel Comics merchandise in tribute to the journalist's passion for both.
Members of the National Union of Journalists formed the guard of honour.
Her family has paid tribute to a "gentle, innocent soul" whose "desire to bring people together made her totally apolitical".
Journalists in RTÉ gathered at 1pm and joined in a round of applause in a symbolic action of solidarity with Ms McKee.
Journalists also posted tributes on social media with the hashtag #WeStandWithLyra.
US Congressman Richard Neal has also condemned the murder of Ms McKee.
Mr Neal is the co-chairman of the Congressional Friends of Ireland Caucus and the Chairman of the House Ways and Means Committee.
Last week, he visited Ireland and Northern Ireland as part of the congressional delegation led by the Speaker of the House Nancy Pelosi.
In a statement, Congressman Neal described the murder as a cowardly act that must be condemned in the strongest possible terms.
"Lyra represented the future of Northern Ireland while the perpetrators of this senseless crime represent the past," he said.
"Twenty one years after the signing of the Good Friday Agreement, there is simply no justification for violence of any kind. And groups like the "New IRA" have no support on either side of the Atlantic," he added.
The 'New IRA' is an amalgam of armed groups opposed to the peace process and it recently claimed responsibility for parcel bombs sent to London and Glasgow in March.
The PSNI believe the violence in Derry was orchestrated in response to an earlier search by officers aimed at averting imminent trouble associated with the anniversary of the Easter Rising.
Speaking earlier on RTÉ's Morning Ireland, NUJ General Secretary Seamus Dooley said Ms McKee had already accomplished an enormous amount of work, and it was easy to say she had a bright future ahead of her.
Mr Dooley said he was shocked and his heart sank when he heard what had happened.
"I think like everyone else I was just full of despair, but also there's a great sense of hope because her family want to treat today as a celebration of her life and we have been told we have to be part of that dignified celebration," he said.
Mr Dooley said over the last few days he has got to know her family and it was very difficult to think that they had lost a daughter, a partner and a sister.
A vigil organised by the Mid-Ulster Trade Union Council will be held in Cookstown, Co Tyrone, to coincide with the funeral service.
Council chairman Harry Hutchinston said the vigil is a mark of respect to Ms McKee, who he said was a natural advocate for young people.