A series of security alerts at buildings due to host three police recruitment events has caused widespread disruption.
Belfast Metropolitan College, the Strule Arts Centre in Omagh and the Waterfoot Hotel in Derry have all been evacuated, with streets around them also sealed off.
The Belfast and Omagh venues, which are in central locations, were set to host PSNI recruitment information sessions on Saturday.
A similar event organised for the hotel on Derry's Waterside on Saturday had already been postponed for a week amid police fears a planned republican protest would disrupt a wedding at the same venue.
The security alerts have triggered significant traffic disruption and has also affected many workplaces. Most of Omagh town centre was evacuated.
Those responsible have been roundly condemned.
Policing Board chairman Anne Connolly said: "It is disappointing that the venues scheduled to host a number of PSNI information sessions for the latest recruitment campaign have been the subject of security alerts.
"However, past experience has shown that intimidation and threat won't stop people choosing policing as a career and we know that there are already a large number of applications submitted for this latest competition.
"Those behind these alerts have simply caused inconvenience to a large number of people who have had to be evacuated from the venues and surrounding areas."
Sinn Fein West Tyrone MLA Barry McElduff said: "Those behind this campaign need to come forward and supply a spokesperson to explain these actions. To date they have failed to do so as they are wrapped up in their own destructive agenda.
"These actions serve no republican agenda, of that I am certain.
"It is high time they stop these activities and catch up with the rest of society."
DUP Policing Board member Jonathan Craig said those wanting to drag Northern Ireland backwards would not win.
"They want to spread that fear amongst people considering a career within the police service but we can all stand together to make sure they do not succeed," he said.
A controlled explosion was carried out on a suspicious object in Derry and subsequently declared to be a hoax. The security operations in Belfast and Omagh continued.
PSNI assistant chief constable Mark Hamilton said: "Police have been responding to concerns that devices may been left at the venues where we are hosting familiarisation events as part of our recruitment campaign. Earlier today police evacuated the Strule Arts Centre in Omagh, the Waterfoot Hotel in Derry and Belfast Metropolitan College.
"A suspicious object was found in the grounds of the Waterfoot Hotel and a controlled explosion was carried out. An examination was carried out on the object and it was declared an elaborate hoax. This device was deliberately placed to cause disruption to the hotel, its patrons and the wider community in Derry and must be condemned by all who strive to achieve success and prosperity for the city.
"Police remain at the scene in Derry and the alerts in Omagh and Belfast unfortunately look set to continue into the night.
"We have been working closely with the venues who are hosting the events and the two planned for Omagh and Belfast tomorrow, will go ahead as scheduled. The Derry event has been postponed until next Saturday, October 17 .
"These are shameless acts that demonstrate no regard for the people living and working in these areas and have been designed to disrupt communities.
"I am aware of the disruption that has been caused by this security operation and I would like pay tribute to all the communities who have co-operated and worked with our officers to ensure disruption was minimal.
"I would strongly encourage everyone to come along to one of the familiarisation events taking place and find out more about the opportunities that exist within the police service.
"As part of our recruitment campaign, we are looking for people who want to make a positive contribution to Northern Ireland and are committed to making a difference.
"We are committed to ensuring that the police service is reflective of our society and welcome applications from across all sections of the community."