Two arrests were made under the Terrorism Act. A 29-year-old man was arrested in Newtownards and a 53-year-old man was arrested in Hillsborough.
A 30-year-old man was also arrested in Newtownards on suspicion of arson with intent to endanger life and possession of a Class B controlled drug.
All three remain in custody at this time.
A number of searches were conducted in the Newtownards area as part of the ongoing operation. A number of items were removed for further examination.
Police continue to appeal to the community to help the investigation and provide any information they have on who might be responsible for these attacks by calling on 101 or 999 in an emergency
