A reward of up to £10,000 has been offered for information leading to the conviction of those responsible for the murder of journalist Lyra McKee.
Ms McKee, 29, was shot in the head last Thursday while observing rioting in Londonderry, and hundreds of mourners attended her funeral on Wednesday.
Police said the Crimestoppers reward might help "assist in efforts to get justice for Lyra and her loved ones".
A dissident republican group, the New IRA, has said its members killed her.
A spokesman for Crimestoppers - a charity which takes calls confidentially via a telephone or using an anonymous online form - said the murder had sent "shockwaves" across Northern Ireland and attracted "global condemnation".
Det Supt Jason Murphy said police had received "widespread public support to date" - more than 140 people have already contacted investigators via the Major Incident Public Portal.
"I want to find the people who murdered Lyra and the information that can help us bring Lyra's killer to justice lies within the local community," he said.
"People saw the gunman - people know who is responsible. I'm asking them to come forward and help us."
Three people have been arrested over the murder, and all have been released without charge.
Prime Minister Theresa May, President of Ireland Michael D Higgins, Taoiseach (Irish prime minister) Leo Varadkar and other politicians were among the congregation at St Anne's Cathedral in Belfast.
Mourners heard that Ms McKee revealed plans to propose to her partner Sara Canning just hours before she was murdered.
Priest Fr Martin Magill received a standing ovation when he asked why it took her death to unite political parties.
Northern Ireland Secretary Karen Bradley has said she intends to hold discussions with Stormont's party leaders this week in a bid to restore power-sharing, following the murder of Ms McKee.
Northern Ireland has been without a functioning devolved government since January 2017.
However, Democratic Unionist Party (DUP) MP Sammy Wilson has said he is not convinced that the murder of Ms McKee has marked a turning point.
Mr Wilson told BBC News NI that Mrs Bradley would "get nowhere" if she "continues to simply talk to people".
Why is Crimestoppers offering a reward?
Jonathan Ireland, Crimestoppers board member, explained the process to Good Morning Ulster
"Someone out there knows exactly who killed Lyra but they haven't come forward yet because they're scared. They don't want to "tout" or get retribution.
"We're putting up this reward with a clear message - you don't need to be frightened.
"You are anonymous. We aren't the police - we are totally separate and when you call the 0800 number or website you are anonymous.
"You'll never be asked your name or address and we cannot trace your number or IP address.
"This is a very high profile murder case that has sent shockwaves across Northern Ireland and the world.
"It's really important this information comes forward and it hasn't and so the decision was taken that a reward would be offered.
"It has been done in the past and it has been successful."
DUP leader Arlene Foster, who held talks with the NI secretary and Irish Foreign Minister Simon Coveney on Wednesday, said she wanted to see the government "take steps" to ensure talks commence.
She added that the DUP wanted to see the assembly restored immediately, alongside a time-limited process dealing with outstanding issues.
Sinn Féin leader Mary Lou McDonald said her party was "ready to play our full part in a serious and meaningful talks process which removes obstacles to power-sharing, delivers rights and restores the assembly".
"Sinn Féin wants to see the full restoration of the institutions of the Good Friday Agreement," she said.
She said Sinn Féin had told Mrs May and Mr Varadkar "that the current situation of stalemate of no executive or assembly is untenable and cannot continue".
"The two governments should now meet with urgency through the British-Irish Intergovernmental Conference, to provide solutions to the outstanding rights issues, which are at the heart of sustainable power-sharing," she added.