Police have confirmed four explosives recovered from Derry City Cemetery Cemetery in Creggan were viable pipe bombs.
It follows trouble in the city over the Easter period, with police coming under attack by youths throwing petrol bombs on Monday.
Derry City & Strabane Area Commander Chief Superintendent Nigel Goddard said: "These actions have seen the exploitation of young people in the illegal parade, with a complete disregard for public safety. We believe these would have been used to attack police, and cause injury to our officers.
