Two teenagers have been arrested by police in connection with the murder of journalist Lyra McKee in Northern Ireland.
The men, aged 18 and 19, were detained under anti-terrorism legislation and have been taken to a police station in Belfast for questioning, the Police Service of Northern Ireland (PSNI) said.
Ms McKee, 29, from Belfast, was shot in the head by suspects police believe were dissident republicans linked to the New IRA during disturbances in Londonderry on Thursday night.
Police have released footage that appears to show a masked shooter firing a handgun towards police and onlookers including Ms McKee during clashes with police on the Creggan estate.
Ms McKee’s death has sparked an outpouring of grief, with tributes led by her partner Sara Canning who said: "Our hopes and dreams and all of her amazing potential was snuffed out by this single barbaric act," she said.
"Victims and LGBTQI community are left without a tireless advocate and activist and it has left me without the love of my life, the woman I was planning to grow old with," she added.
"This cannot stand, Lyra's death must not be in vain because her life was a shining light in everyone else's life and her legacy will live on and the life that she has left behind."
Ms McKee was an editor for California-based news site Mediagazer and in 2016 was named by Forbes Magazine as one of their 30 under 30 in media.
She had been working on a new book which had been due to be published in 2020.
Political leaders including Prime Minister Theresa May and Taoiseach Leo Varadkar joined to condemn the murder.
"My deepest condolences go to her family, friends and colleagues," Mrs May said. "She was a journalist who died doing her job with great courage."
Mr Varadkar added: "We cannot allow those who want to propagate violence, fear and hate to drag us back to the past."
Heartbroken by the murder of Lyra McKee and the violence in Derry. The challenges in NI today are real--but we cannot let go of the last 21 years of hard-won peace and progress. This tragedy is a reminder of how much everyone has to lose if we do.— Bill Clinton (@BillClinton) April 19, 2019
Former United States president Bill Clinton tweeted: "Heartbroken by the murder of Lyra McKee and the violence in Derry.
"The challenges in NI today are real-but we cannot let go of the last 21 years of hard-won peace and progress. This tragedy is a reminder of how much everyone has to lose if we do."
Tributes to Ms McKee include Michelle Stanistreet, National Union of Journalists (NUJ) general secretary, who said Ms McKee was one of the most promising journalists in Northern Ireland.
Northern Ireland Secretary Karen Bradley, speaker of the US House of Representatives Nancy Pelosi, DUP leader Arlene Foster and Sinn Fein deputy leader Michelle O'Neill were also among those to pay tribute.
Police, who described the shooting as a "terrorist incident", believe the violence was orchestrated in response to an earlier search by officers aimed at averting imminent trouble associated with this week's anniversary of the Easter Rising.
Around 50 petrol bombs were thrown in the confrontation and two cars were burned out.
Officers believe more than one person was involved in the murder.
Detective Superintendent Jason Murphy, who leads the inquiry, described the murder as "senseless and appalling beyond belief".
"People saw the gunman and people saw those who goaded young people out onto the streets, people know who they are," he said.
The New IRA is an amalgam of armed groups opposed to the peace process and recently claimed responsibility for parcel bombs sent to London and Glasgow in March.