A man from North Belfast is understood to have died in Turkey.
It is also believed that two friends with whom he was travelling have fallen sick.
The Irish Government said it is aware of the case and is providing consular assistance to the families.
A spokesperson for the Republic of Ireland’s Department of Foreign Affairs told Belfast Live: “We are aware of the case and are providing consular assistance.”
It is understood two of the men were travelling on an Irish passport, while the third is thought to be in the country on a UK passport.
A UK Foreign & Commonwealth Office spokesperson said they have not yet been contacted for help.
The Kevin Bell Repatriation Trust are believed to be assisting.
North Belfast Sinn Fein councillor JJ Magee told Belfast Live: "The Ardoyne community is in a state of shock as this tragic news filters through tonight.
"Friends of the families don't have very much information. We are hearing two young people are seriously ill and one young person has died.
"Our thoughts are with their family and we are here to help the family in any way that we can during this terrible time."
Belfast Deputy Mayor, SDLP councillor Paul McCusker, said: "Worrying and devastating news coming from Turkey regarding three local North Belfast men.
"At this stage we know one male has died and two others are critical.
"As a North Belfast community all our thoughts and prayers are with you all including the families."
