Between 30,000 to 50,000 Norwegians, commonly labelled the "German girls", were involved with occupying troops during World War II, according to estimates from Norway's Centre for Holocaust and Minorities Studies.

As well as public humiliation, many of the woman were subject to reprisals by officials after the 1945 liberation from Nazi occupation, including illegal arrests and detentions, job dismissals and even being expelled and stripped of their nationality.

"Young Norwegian girls and woman who had relations with German soldiers or were suspected of having them, were victims of shameful treatment," Norway's Prime Minister Erna Solberg said.

"Today, in the name of the government, I want to offer my apologies," the premier said at an event to mark the 70th anniversary of the UN's universal declaration of human rights.

"For many, this was just a teenage love, for some, the love of their lives with an enemy soldier or an innocent flirt that left its mark for the rest of their lives."

During the war, more than 300,000 German soldiers occupied Norway, a neutral country the Nazis invaded on April 9, 1940. Heinrich Himmler, the Nazi SS chief, considered Norwegians "goddesses" and encouraged his troops to have relations with local women.

The first "Lebensborn" reproduction centre outside Germany was set up in Norway in 1941 as part of the Nazi Aryan race ideology.

In 2000, Olso formally apologised to the estimated 10,000 to 12,000 children born to Norwegian mothers and German soldiers, who also suffered reprisals.

- People in the street -

More than 70 years after the end of WWII, very few of the women remain alive and the official apology is unlikely to open the way for financial reparations for their families.

"The people directly affected are no longer with us... but this also touches their families and the children," said Reidar Gabler, son of a Norwegian woman who was expelled in 1945 along with her German husband.

"Even if it comes late, the apology is important for history," he told Norway's Aftenposten newspaper

Historian Kare Olsen said he was unaware of any similar apology in other European countries where women suffered after their involvement with soldiers during German occupation.

Thousands of French women were publicly shorn after the liberation; some were detained or executed in what were mostly extrajudicial reprisals.

"In France, for example, these women were mistreated after the liberation, but it was more by people in the street than by the authorities," Olsen said.

In Denmark, historians estimate the number of woman involved with members of the German occupying forces was around 50,000 but there were no accusations or forced expulsions.

"There is less reason for an official apology than in Norway," said Anette Waring, a professor at the Danish University of Roskilde.

None of the estimated 28 Norwegian men married to German women during the war were expelled or had their nationality taken away from them, according to historian Guri Hjeltnes, the director of the Holocaust and Minorities Studies centre.

"We cannot say women who had personal relations with German soldiers were helping the German war effort," Hjeltnes said. "Their only crime was breaking the unwritten rules."