Petrol bombs and other missiles have been thrown at police in Londonderry, where a security alert is underway in the Creggan.
A suspicious object has been found during searches on Monday, as part of investigations into dissident republican activity.
Around 80 officers and explosive detection dogs have been searching for bomb-making equipment, following the discovery of a mortar bomb in Strabane at the weekend.
Police have blamed the New IRA for the viable device and have said the members responsible are “living in the community - they are building bombs and storing weapons and placing the community at risk”.
Officers in the Creggan are appealing to parents to remove their children from the vicinity of their operation “to prevent anyone getting drawn into disorder”.
Several homes in the Creggan Heights area have been evacuated due to the alert and the area from Rathmore roundabout to Fanad Drive has been sealed off.