DUBLIN—A pug-nosed Belfast dog named Lennox, who inspired a two-year legal fight and animal-rights protests on both sides of the Atlantic, has been put to sleep by city officials.

Belfast City Council confirmed the 7-year-old dog was put down Wednesday after a deadline for legal appeals expired.

Dog wardens deemed the pit bull-type dog to be a public danger and seized him from his owners in April 2010. Northern Ireland’s senior appeals court last month upheld two 2011 court rulings that Lennox should be put down.

His owners argued that Lennox was not even a pit bull, never attacked anyone and could be resettled outside Northern Ireland rather than killed. An online “Save Lennox” petition and social media campaign spurred protests in Belfast and New York seeking his freedom.