Lyra McKee murder: Politicians united in their condemnation
The Prime Minister led condemnation of the murder of Lyra McKee, describing it as "truly senseless".
Theresa May was speaking as politicians from across Ireland and the UK joined in criticising the brutal killing of the young journalist.
It included a rare joint statement from six Northern Ireland party leaders.
Mrs May said: "The death of Lyra McKee in the suspected terrorist incident in Londonderry is shocking and truly senseless.
"My deepest condolences go to her family, friends and colleagues. She was a journalist who died doing her job with great courage."
Labour leader Jeremy Corbyn called the murder "senseless".
"This shocking attack is a reminder of the vital importance of protecting the Good Friday Agreement and Northern Ireland peace process," he said.
Secretary of State Karen Bradley said that she was "deeply shocked and saddened".
"Those responsible for last night's violence have nothing to offer anyone in Northern Ireland," she said.
"Their intolerable actions are rejected by the overwhelming majority of people who want to build a peaceful and more prosperous future for everyone in Northern Ireland."
In a joint statement, the leaders of the six main political parties here said it was an attack on the peace process.
The statement was issued by Arlene Foster of the DUP, Sinn Fein's Michelle O'Neill, Robin Swann of the UUP, Colum Eastwood of the SDLP, Alliance's Naomi Long and Clare Bailey of the Green Party
They said: "We want to express our condemnation in the strongest terms possible at the murder of journalist Lyra McKee.
"The murder of Lyra McKee is first and foremost a devastating loss for her grieving partner, family and friends, and our thoughts are with them at this awful time.
"Lyra's murder was also an attack on all the people of this community, an attack on the peace and democratic processes.
"It was a pointless and futile act to destroy the progress made over the last 20 years, which has the overwhelming support of people everywhere.
"We are united in rejecting those responsible for this heinous crime.
"They have no support in the community, must be brought to justice and should disband immediately.
"We reiterate our support for the PSNI, who while carrying out their duties were also the target of last night's attack.
"We call on anyone with any information to bring that forward to the police and assist their enquiries."
Attending a vigil for Ms McKee in Derry yesterday, Mrs Foster urged Catholics and Protestants to come together in the wake of the murder by dissident republicans.
"Of course this is not the first time I have been in this wonderful city, but it is the first time I have been in this part of this wonderful city," the DUP leader said.
"I want to say your pain, is my pain. It doesn't matter whether you are Catholic or a Protestant. Whether you identify as Irish or British.
"When people come out with guns to shoot people from their own community, then we have to say: enough is enough."
Sinn Fein president Mary Lou McDonald, who was also at the vigil, said: "These so-called dissident groups who took her life offer nothing, only hardship and suffering.
"They do not represent the community, the people of Derry or wider opinion."
Taoiseach Leo Varadkar led condemnation from the Irish Government.
He said that those behind the murder were "cowards who will fail in their hate-filled efforts to drag Ireland into the past".
In a statement outside Government Buildings in Dublin, he added: "An activist and journalist, she changed lives as she lived and will do so again in death."
A senior US politician has also expressed her sadness at the murder. Nancy Pelosi, who is the Speaker of the US House of Representatives, made her comments during a visit to Stormont to mark the anniversary of the signing of the Good Friday Agreement.
A moment of silence was held at Stormont's Long Gallery in memory of Lyra.
Assembly Speaker Robin Newton told of his hope that those responsible would be brought to justice.
Ms Pelosi and her delegation of US congressmen and women were on the final day of a four-day visit to the island of Ireland.
On Thursday they had visited Derry, just hours before Ms McKee was shot.
Ms Pelosi extended her condolences to her family.
"Sadly Mr Speaker, we join you on the sadness of the tragedy that happened last night," she said.
"We extend our condolences to the family, and your moment of silence at this time, on Good Friday, is especially poignant.
"You not only had a moment of silence, you presented a sense of resolve that justice would be done and the memory of that young woman would be a lesson for all of us."