McDonald's was forced to apologize and halt a Halloween-themed campaign which featured the slogan "Sundae bloody sundae," Portuguese and Irish media reported on Thursday.

The slogan was inspired by a 1982 song by the Irish rock band U2 "Sunday Bloody Sunday." The song focuses on the emotional fallout of a 1972 massacre in Derry/Londonderry by British troops who killed 14 civilians and injured 26 more. The event took place during a Sunday protest rally and was dubbed "Bloody Sunday."

McDonalds Portugal said the ad campaign was only used by a "small number" of local restaurants.

Read more: At Irish border, Brexit evokes history of violence

'Ignorance is the new cool'

"The campaign was intended as a celebration of Halloween, not as an insensitive reference to any historical event or to upset or insult anyone in any way," a spokesman was quoted as saying by the Belfast Telegraph.

"We sincerely apologize for any offense or distress this may have caused," he added. "All promotional material has been removed from restaurant."

Social media users slammed the campaign online with images spreading on Twitter.

"Hate to do this to you McDonalds but Sunday Bloody Sunday is actually about a massacre that happened in Derry in 1972," Irish reporter Fintan Walsh wrote on Twitter, paraphrasing a comedy sketch featuring fictional TV presenter Alan Partridge.

"Ignorance is the new cool," another user posted.

The restaurant chain had removed all advertising material linked with the ad, according to Portuguese daily Correio da Manha.

Another massacre in Ireland, when British troops opened fire on the crowd at a Gaelic football match in Dublin's Croke Park stadium  in 1920, is also referred to as "Bloody Sunday."

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