Police believe dissident republicans may be responsible for a "viable postal device" which was delivered to a hotel in Londonderry.

Ammunition Technical Officers (ATO) were tasked to the hotel at Ebrington Square in the Waterside after the package was discovered at about 15:20 GMT on Tuesday. They carried out a controlled explosion on the device, which was later taken away for a forensic examination.

Police Service of Northern Ireland (PSNI) Chief Supt Gillian Kearney condemned it as "shameful and utterly abhorrent", adding that "those responsible clearly do not care who or what they harm".

"We are keeping an open mind as to who is responsible, and we are working through a number of lines of enquiry, one of which, at this time, is that dissident republicans may be responsible," Kearney said.

She said the investigation was at an early stage and has appealed to anyone with information to come forward as "it could make all the difference". A number of people were evacuated from The Ebrington hotel, along with staff from neighbouring premises.

The chair of a local policing watchdog said he believed it may be linked to the Ministry of Defence (MoD) having a stall at a careers fare at the same hotel last month. A Halloween funfair had been taking place a short distance away from the hotel. It remained open during the security alert.

Toni Collins said the targeting of The Ebrington was a "disgrace" especially in the run up to Halloween when thousands would be in the city. "No-one wants it and no one supports it," she said.

Teresa Boyle from Enniskillen is visiting the city. She said the community had moved on and no-one wanted to return to the conflict of the past. "That's what people want, peace," she added.

Mayor of Derry City and Strabane District Council councillor Grace Uí Niallais said her "thoughts are with the staff and anyone impacted".

"This was a serious and reckless incident which has no doubt caused trauma to all involved. We will not go back to the past but instead look forward to the fantastic four days of Halloween celebrations ahead," she said. Justice Minister Naomi Long condemned the incident, calling it "abhorrent". "The viable device was placed in the vicinity of families and young people celebrating Halloween," she said.

"It was an utterly shameful and dangerous act and the people behind it have shown absolutely no regard to the community or businesses affected." She paid tribute to the police officers who responded to the incident, "once again putting themselves in harm's way to ensure the safety of the public".

Secretary of State for Northern Ireland Sir Chris Bryant said it was "very worrying".

He added: "This is absolutely despicable. Whoever has been involved in this, I very much hope that we'll be able to track down who it is, and they should face the full force of the law." Ulster Unionist councillor Darren Guy, who chairs the local policing and community safety partnership, believes the incident was timed to cause maximum disruption. He also said it may have been linked to the MoD being represented at a careers event at the hotel in September.

"Recently, there was a careers event held in that hotel where I believe an RAF [Royal Air Force] stall was there for the careers event at that time.

"This was specifically done this week to cause as much disruption as possible during the 40th Halloween celebrations with thousands of international visitors visiting the city and the amount of families, especially young families going out to enjoy the many things on offer.

"It is totally reckless and these people don't think about anyone else but themselves." Sinn Féin councillor Christopher Jackson said it was too early to "speculate" about any link between the alert and the jobs fair. "We need clarification from those responsible," Jackson said. He said this was "a disgusting attack on the city and the people of Derry".

"There is no justification whatsoever for carrying this out and putting people in danger, especially when the city is gearing up for the 40th anniversary of the Halloween festival," he added.

"Derry is a warm and welcoming place and it's disgusting why someone or some organisation did this." Foyle SDLP MP Colum Eastwood told BBC Radio Foyle's North West Today programme the incident must have been terrifying for those members of the public in the vicinity of the hotel .

"This was clearly a viable device which is really frightening for the staff and the visitors to the hotel and to the hundreds, probably thousands of kids who were at that funfair yesterday and have been over the past number of days," Eastwood said.

"I don't know what entered someone's head to think this was a good idea.

"It is appalling, reckless and achieves absolutely nothing." Julie Middleton, Democratic Unionist Party (DUP) assembly member for Foyle, told BBC Radio Ulster's Good Morning Ulster programme on Wednesday that she was "deeply disturbed and disgusted".

"There is no excuse to leave a viable device anywhere at all, but in the middle of Ebrington Square, where you have people at their work, families out enjoying some half-term fun and tourists visiting and unfortunately this was designed to cause disruption and with any viable device, it was obviously designed to cause harm," she said.

The Police Federation for Northern Ireland (PFNI) described sending a viable device to a hotel as "the height of madness".

"If this device had detonated, there's no knowing the damage it would have done," PFNI chair Liam Kelly said. "Not for the first time at the hands of these reckless fools, innocent lives were put at risk."

Kelly said those responsible were "reckless thugs" who wanted to "kill and maim", but that there was an "utter futility to their efforts to destabilise society."