According to Swedish police, one member of the organisation, which has links to far-right groups, was taken to hospital after some type of fluid was splashed into their eye.
Others filed reports to the police claiming they had been punched and kicked.
“We really do not know the origin of the quarrel, but those who have been victims of punches and kicks and have filed these reports all say that they belong to the Soldiers of Odin organisation, police spokesman Christer Fuxborg told TT newswire.
It remained unclear whether the brawl had taken place during one of the group’s night patrols, which they claim are necessary to protect Swedish citizens, particularly women, from violent attacks and sexual assaults carried out by immigrants.
Another Soldiers of Odin patrol took place in Uppsala on Saturday night, without causing any problems.
“There were about a dozen of them who came here… which of itself probably was not a major problem,” said Nina Dahlström, duty officer with the Uppsala police. “It could have been a problem if we had had 20 or 30 from the left wing who had come along and wanted a fight.”
Uppsala police had contacted left-wing groups asking them not to mount counter-demonstrations, she said.
Soldiers of Odin, founded by Finnish Nazi Mika Ranta, has previously conducted patrols in Borlänge, Trelleborg and Stockholm.
Several of its Swedish members have been convicted of serious crimes and Nazi sympathies, according to an investigation by Expo magazine.
Two Muslims ahead of booze cruise rape trial
The men, both aged 19, were arrested after the M/S Galaxy docked in Stockholm on Wednesday, accused of gang-raping a girl during a drunken booze cruise across the Baltic.
A third man, aged 18, was released after the court ruled there was insufficient evidence to keep him behind bars.
Martin Beskow, defence lawyer for one of the 19-year-old men, told Aftonbladet that his client was disappointed that he had not been given a chance to give his side of the story.
“This was upsetting for my client. The court thought that there was reasonable grounds for suspicion. I did not,” he said.
Åke Broné, who was defending the released 18-year-old, told the newspaper that his client denied having sex with anyone during the cruise, forced or otherwise.
“He went back and forth to his cabin, but he didn’t have any sex. Instead my client was just hanging around with other mates,” he said.
Around 1,700 students were on the Fun Cruises party boat from Stockholm to the Finnish town of Turku, with police accompanying them on the Silja Line’ ferry to maintain control.
Sweden-Finland ferry crossings are notorious for heavy drinking, as all passengers over the age of 18 are able to buy duty free alcohol, meaning a huge discount for Finnish and Swedish travellers used to some of the highest food and drink taxes in Europe.
Four men were arrested after the ferry docked on Wednesday and a fifth on Thursday, but two were released on Friday evening after the police judged there were no longer any grounds for suspicion.
Sweden’s Aftonbladet newspaper, which by chance interviewed two of the men as they departed on the cruise, reported last week that one had a previous conviction, while two were already under investigation for allegedly aiding and abetting a murder in Stockholm.
The rape case has been seized upon by Sweden’s fast-growing right-wing media as evidence of the dangers of immigration, with the Fria Tider newspaper reporting that the 19-year-old man interviewed by Aftonbladet was “a non-European immigrant”, while his companion was “an immigrant who is not a Swedish citizen”.
“We’re going to fuck around,” one of the men told Sara Cosar, an Aftonbladet reporter before the ship departed. “We’re graduating, so we just want to fuck around.”
Cosar, who was on the cruise, said that there had been “a great atmosphere” on board, as students let their hair down.
Fun Cruises, which organised the event, billed it as “a crazy action packed day at sea” on a “ship filled with students from all over the country”.
What Sweden is doing to crack down on terrorists
The new laws come just over a week after more than 30 people were killed in a series of suicide bombings in the heart of the EU at Brussels’ Zaventem airport and the underground station Maelbeek.“With last week’s horrific attacks in Brussels fresh in our minds, it feels very good that from today onwards, we have a new, tougher legislation in place which gives the security services more muscle to prevent terrorist crimes in Sweden,” Prime Minister Stefan Löfven told reporters.
The anti-terror legisation, which was voted through in parliament in March and toughens existing legislation, will punish those who travel abroad to join a terrorist group.
Those convicted of travelling to another country to seek training or to commit a terrorist act will be handed two-year sentences.
The law also stipulates that those who finance a terrorist group must spend up to two years behind bars, or up to six years if the crime is considered aggravated, reported the Aftonbladet tabloid.
Sweden’s intelligence service Säpo has previously identified around 300 people as having left Sweden since 2013 to join the Isis jihadist group in the Middle East. It believes 135 have since returned to Swedish soil and has said returning fighters are among the biggest threats to Sweden.
Löfven also said he wanted to increase funding to the agency.
“We are also giving a new assignment to the security police to tighten controls of those who return from terror travels. If someone is planning an attack in Sweden we will do everything to stop them,” he said.
Sweden recently lowered its terror threat level down to three (on a scale from one to five, where five is the highest) after raising it briefly in November, days after the attacks in Paris left 130 people dead and during a separate hunt for a suspected terrorist in the Nordic country.
However the terror suspect police arrested soon afterwards in northern Sweden turned out to be innocent and later demanded compensation from the Swedish government.