Police in Northern Ireland have launched an investigation after footage surfaced of a man wearing a balaclava and allegedly holding an assault rifle while singing the Irish rebel tune "Come Out Ye Black and Tans". 

The video, which was posted on social media on two occasions on December 29 and 30, appears to have been filmed in a pub in Belfast, although the pub has not yet been identified. 

A scarf from the north Belfast soccer team, Cliftonville, which boasts strong nationalist roots, can be seen hanging from the pub's ceiling during the video. 

Meanwhile, a man with a strong Ulster accent can be heard describing the man as a "maniac" during the video. 

The PSNI has told the UK outlet the News Letter that it is investigating the incident. 

"Police in north Belfast have received a report of a video circulating on social media and are currently investigating the circumstances," the PSNI told the publication. 

Brian Kingston, a DUP MLA for North Belfast, condemned the footage and told the  News Letter that he has reported the incident to the police. 

"If this is meant as a joke, it is in extremely poor taste and is deeply hurtful to victims of terrorist violence," Kingston told the Newsletter. 

"I have brought this to the attention of the PSNI in North Belfast, not least as the nature of the weapon being brandished requires investigation.

"It is incumbent on the owner of these premises to ensure there is no repetition of such behavior in a crowded public bar." 

Written by Irish songwriter Dominic Behan in the 1960s, "Come Out Ye Black and Tans" is a hugely popular rebel song in Ireland and among the nationalist community in Northern Ireland. 

The song's title references the Black and Tans, who were notoriously brutal during the Irish War of Independence.