District Commander Superintendent Gordon McCalmont said: "It is our assessment that the New IRA is responsible for the mortar device that was discovered outside homes in Church View Close in Strabane on Saturday morning.
"The people who left this device had every intention of killing my colleagues serving the Strabane community. They showed no regard for the families, elderly and vulnerable people who were forced to leave their homes and whose lives were put at risk.
"As a parent myself it was terrifying to hear local mother Aileen Mullan recount how close her children were to this deadly device.
"The New IRA members behind this attack are living in the community. They are building bombs and storing weapons and placing the community at risk. To further highlight the recklessness and total disregard shown by the New IRA, a public safety operation is taking place in Creggan this morning involving approximately 80 officers and explosive detection dogs.
"Our assessment is that this group is concealing bomb making materials. We have a number of areas of focus but there is nothing definitive and no guarantees. However, our chances of success are vastly improved by support and information from the community.
"Our focus will remain on keeping the community safe against the threat posed by these violent groups and I would strongly urge people to report any suspicions they have about dangerous and illegal activity in our community."