A military grade assault rifle has been discovered in Strabane, police said
Superintendent Mark McEwan said the Armalite-type weapon had been intended for an attack on officers.
The gun was found with ammunition during a security alert at Lismourne Place on Friday as part of an investigation into new IRA activity.
Mr McEwan said: "We believe this was brought into the area in an attempt to carry out an attack on police.
"That would have been an attempt to kill police officers, but the calibre of this weapon is such that it is capable of penetrating walls, so any type of attack carried out using this weapon is totally regardless of the safety of the community.
"People in their own homes would not have been safe if this weapon was fired in a built-up area.
"Those who were intent on using this weapon have no concern whatever for the safety of the community."
He said the find would be subjected to a full forensic examination, but at this stage it was believed to be "the real thing".
He also appealed for anyone who had information about this particular weapon, or any suspicious activity, to contact police at Strand Road or Crimestoppers.
The new IRA is believed to have been formed in 2012 from an amalgamation of previously separate dissident republican organisations.
SDLP West Tyrone MLA Daniel McCrossan described the firearm find as "deeply worrying".
Mr McCrossan said: “This discovery of this weapon is a deeply worrying development. Illegal and irresponsible gun ownership is very dangerous and we have seen weapons of this type used in illegal activity including the attempted murder of police.
“The illegal storing of firearms is unacceptable and it allows those who committed to violence to continue to put the public at risk. We must all be vigilant against this threat and I would encourage anyone with any relevant information to contact the police immediately.”
West Tyrone Ulster Unionist MLA Ross Hussey said the find raises further doubts about the IRA decommissioning process.
Mr Hussey, who represents his party on the Policing Board, said: "For some time now I have questioned the decommissioning of weaponry by the IRA. I am convinced that there were groups within the Provisional IRA that did not comply with the decommissioning instructions and instead retained some of the weapons and ammunition that were under their control.
“The fact is that we do not know what was decommissioned and we certainly have no list of what was not. The Police have described the weapon recovered on Friday evening in Strabane as an armalite-type assault rifle which belonged to the group styling itself the ‘New IRA.’
"This concerns me greatly as it is clearly is a weapon with great firepower and was brought into the area to kill a member of the security forces. Past experience tells us that there is also a threat to the public, not least if a child were to come across it."
He added: “The price of safety is indeed eternal vigilance, and once again I pay tribute to all those members of the security forces, in the United Kingdom and the Republic of Ireland, who through their dedication to duty and bravery, protect and defend us all.”