Former US President Bill Clinton has issued a statement following the death of journalist Lyra McKee.
Mr Clinton, who was heavily involved in the deal which led which led to the Good Friday agreement in 1998, said "we cannot let go of the last 21 years".
He tweeted: "Heartbroken by the murder of Lyra McKee and the violence in Derry.
Lyra McKee murder probe detectives arrest two teenagers
"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."
He tweeted the statement to his 11 million followers on Friday night.
Detectives have arrested two men in connection with the murder of Miss McKee.
The teenagers have both been taken to Musgrave Serious Crime Suite.
They have been arrested under the Terrorism act.
Lyra McKee murder: PSNI release chilling CCTV footage of gunman
A PSNI spokesman said: "Major Investigation Team detectives have arrested two men, aged 18 and 19 under the Terrorism Act, in connection with the murder of Lyra McKee in the Creggan area of Derry on Thursday, 18th April.
"They have been taken to Musgrave Serious Crime Suite."
The 29-year-old North Belfast woman was at the scene reporting on rioting on Thursday night when she was shot.
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