The death of Lyra McKee should mark a new beginning for Northern Ireland, a priest has told mourners.
Dissident republican gunmen who killed the Belfast-born journalist, 29, should lay down their arms, Father Martin Magill added.
He urged politicians at Northern Ireland's suspended powersharing administration in Stormont to work together to produce a better life for young people.
Fellow journalists formed a guard of honour as the service for their murdered colleague began in Belfast.
Taoiseach Leo Varadkar, President of Ireland Michael D Higgins and Tanaiste Simon Coveney, as well as UK Prime Minister Theresa May and Labour leader Jeremy Corbyn, were among those who attended.
Ms McKee was killed by indiscriminate fire as she observed clashes between police and New IRA dissidents on the Creggan estate in Derry on April 18.
Her funeral was cross-community and mourners spanned both sides of the border.
Family of murdered journalist Lyra McKee pay tribute to 'gentle innocent soul'
Catholic priest Fr Magill said: "I dare to hope that Lyra's murder on Holy Thursday night can be the doorway to a new beginning. I detect a deep desire for this."
The service of thanksgiving was held in the Church of Ireland's St Anne's Cathedral, a short distance from her north Belfast home.
Fr Magill said: "To those who had any part in her murder, I encourage you to reflect on Lyra McKee, journalist and writer, as a powerful example of 'The pen is mightier than the sword'.
"I plead with you to take the road of non-violence to achieve your political ends."
Since the killing many have condemned the culture of violence and coercive control practised by dissidents, the clergyman said.
"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.
Friends of murdered journalist Lyra McKee say New IRA have blood on their hands after brutal killing
"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."
He called on political leaders to break the Stormont negotiations impasse.
"I pray that Lyra's murder may be the catalyst needed for parties to start talking, to reform that which was corrosive in previous assemblies and to begin anew."
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 (NUJ) formed the guard of honour.
The congregation was led by Ms McKee's partner Sara Canning, 35, her mother Joan McKee, 68, brothers Gary and David and sisters Joan, Nichola and Mary.
New IRA offers 'full and sincere' apology for murder of journalist Lyra McKee in Co Derry
Her family have paid tribute to a "gentle, innocent soul" whose "desire to bring people together made her totally apolitical".
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.
Police 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.
