Five men have been arrested by police investigating an illegal parade involving dissident republicans.
Police were pelted with petrol bombs and other missiles ahead of the march in Derry on Monday.
The men aged 29, 31, 42, 45 and 50 were detained after a search of premises in the Chamberlain Street area of Derry on Wednesday.
A number of items were also seized.
Chief Inspector Paul McCracken said: "Immediately after the parade and the attack on local police officers on Monday, we said that robust action would be taken against those who orchestrated the violence and those who participated.
"These searches and arrests are the first phase of that action and more will follow in the coming days.
"Those who seek to attack police and bring violence on to the streets can expect to be held accountable for their actions."
On Monday, six men appeared in court charged over a separate dissident republican parade in Lurgan, Co Armagh, on Saturday.