A dangerous dog at the centre of an international campaign to save it has been put down, Belfast City Council said.
The council's expert described Lennox as one of the most unpredictable and dangerous dogs he had come across.
First Minister Peter Robinson suggested that Lennox, a pit bull-type dog, should be re-homed after an internet campaign for his reprieve went viral. His destruction was ordered by the Court of Appeal last month.
Staff at Belfast City Council have been the target of intimidation by some supporters.
A council spokeswoman said: "Belfast City Council confirmed today that the dog Lennox, an illegal pit-bull terrier type, has been humanely put to sleep.
"Whilst there is an exemption scheme to which dogs of this type (pit-bull terrier type) may be admitted as an alternative to destruction, there were no such measures that could be applied in this case that would address the concerns relating to public safety."
Campaigners claimed to have attracted 200,000 signatures in support of a reprieve. Well-known people including boxer Lennox Lewis and Mr Robinson were among those who used Twitter to call for the dog to be spared.
Protests have become more sinister and workers in Belfast City Council have become the target of a fresh series of intimidating and threatening messages.
Lennox was impounded by Belfast City Council's dog wardens in 2010. He was owned by a disabled woman whose family claimed that he is not dangerous, but while it was unclear exactly what breed he was, pit bulls and dogs like them are illegal in Northern Ireland.
In June, Northern Ireland's most senior judges rejected Caroline Barnes' legal bid to overturn an order for the destruction of her pet. Two lower courts had already ruled that the dog should be put down.
A former Metropolitan Police dog handler claimed the dog represented a danger due to his unpredictability.
Ms Barnes (35) had accepted her pet was a pit-bull type, but claimed there had been a failure to properly consider a possible exemption scheme. The dog's heartbroken owner said her teenage daughter Brooke had been denied the chance to say a final farewell.
"We had told Brooke that even if we don't win (the case), she can still see Lennox, have her last pictures with him and say goodbye," Ms Barnes told the
Belfast Telegraph.
"To then have to tell her that no, that is not happening, it has been extremely unfair."
The family has been told the dog's body will not be returned but they will receive his ashes.
Last night Lennox supporters staged a protest in Spain, following similar rallies in New York and Serbia.
Ms Barnes said: "We can draw a bit of comfort from all of the brilliant friends that we have made."
PA