Four males were arrested under terrorism laws on Thursday in connection with the killing of journalist Lyra McKee in Londonderry last month, Northern Ireland's police force said.
McKee, 29, was shot in the head during a riot in the second largest city in the British province on 18 April.
The act of violence has since been claimed by dissident republican group the New IRA.
"Detectives carried out searches at four houses in the city and arrested four people in connection with the violence which was orchestrated on the streets of Creggan on the evening of Lyra McKee's murder," said Police Service of Northern Ireland senior detective Jason Murphy.
The four arrested, aged 15, 18, 38 and 51, are being held and questioned in Belfast, police added.
The New IRA has apologised over the killing, saying McKee was unintentionally shot as its forces targeted a night-time police raid.
A splinter dissident faction, the New IRA seeks the integration of British-ruled Northern Ireland with Ireland -- rejecting non-violent political campaigns to achieve unity.
McKee established her career writing about so-called "ceasefire babies" -- the generation that came of age after the 1998 Good Friday Agreement, which ended the conflict known as "The