A woman was killed after shots were fired during rioting in Ireland that saw police attacked by petrol bombs and other missiles.
After earlier appealing for calm when a number of shots were fired in the Irish nationalist Creggan area of the city, police confirmed shortly after midnight that the 29-year-old woman had died.
"We are treating this as a terrorist incident and we have launched a murder inquiry," Police Service of Northern Ireland (PSNI) Assistant Chief Constable Mark Hamilton said in a statement.
A local journalist at the scene, Leona O'Neill, wrote on Twitter that after the woman was hit and fell beside a police Land Rover, officers rushed her to hospital, where she died.
Ms O'Neill had earlier posted videos of police vehicles being pelted with what she said were dozens of petrol bombs, bricks, bottles and fireworks.
The videos showed two vehicles were left in the middle of the street and lit on fire.
The rioting was in response to a house search that a large number of officers conducted in the area, she said.
The detonation of a large car bomb outside a courthouse in Londonderry in January highlighted the threat still posed by militant groups opposed to a 1998 peace deal that largely ended three decades of violence in the British-run province. No-one was injured in the blast.
US House of Representatives Speaker Nancy Pelosi led a congressional delegation to the city earlier on the day, as part of a trip to show support for the peace agreement politicians in Washington helped to broker.
The leaders of Northern Ireland's two largest political parties, the Irish nationalist Sinn Fein party and pro-British Democratic Unionist Party (DUP), both condemned the killing.
"Those who brought guns onto our streets in the 70s, 80s & 90s were wrong. It is equally wrong in 2019. No one wants to go back," the DUP's Arlene Foster said on Twitter.