MUA National Secretary and ITF President Paddy Crumlin has marched in - and addressed - this year's May Day rally in Olso, Norway.
Mr Crumlin said this year's May Day in Oslo was particularly poignant - not just for the people of Norway but trade unionists worldwide as the country continues to come to terms with the tragedy which beset the nation last year.
On July 22, 2011, the right wing extremist Anders Breivik set off a bomb outside government offices in Oslo and then went on a gun rampage at a Labour party youth camp on the island of Utoya, killing 77 and injuring several others.
Breivik, 33, admits the killings, but denies guilt or insanity. He went on trial on April 16 in an Oslo courtroom.
May Day this year in Oslo was a record turnout and follows a rally last Thursday in the square close to the court room where Breivik is being tried.
"Right across the world, people were shocked and distressed by the attacks on Norway, its people, its democratic institutions and on the Arbeiderpartiet - the Norwegian Labour Party," Mr Crumlin said.
"That the attack on Utoya was targeted at young people makes such an event even more incomprehensible.
"Many of those attending the youth camp on Utoya were part of the Norwegian trade union movement and shared the values we all hold dear.
"There is no place in a civilized world for such a barbaric act.
"Members of the MUA and the ITF have expressed their grief and sorrow at the events which unfolded."
Norwegian Prime Minister Jens Stoltenberg told newspaper Dagsavisen on Monday that it would be a "different" sort of tribute on May Day this year.
He said the day traditionally meant to glorify workers would have the same goals, which he thinks are more important than ever.
"The first of May will be different this year," Mr Stoltenberg said. "I'll be thinking about the many AUF members who would have been here, marched in the parades and taken part in tributes. I'll go to Bergen, where both the leader of AUF and the deputy leader were killed on Utøya."
Stoltenberg stressed that Labour Day tributes would still highlight the same fundamental values as in every other year, perhaps with even more solidarity and emphasis on freedom and fellowship.
"We've seen that can't just be taken for granted, like we sometimes think," he said.
Labour Day on May 1st is a national holiday, with many Norwegians spending the day attending or speaking at political rallies, marching in parades or simply cheering them on as spectators.
After the rally there was a youth conference which was attended by MUA delegates Sarah Maguire (Qld) and Kyle McGinn (NT).