Wearing black jackets adorned with a symbol of a Viking, Finnish white supremacists the 'Soldiers of Odin' have surfaced as self-proclaimed patriots patrolling the streets for immigrants.

Marching with banners and masks, and claiming to be protecting native Finns from immigrants, fears are now growing about their expanding presence and motivations.

On the northern fringes of Europe, Finland has little history of welcoming large numbers of refugees, unlike neighbouring Sweden.

A member of Soldiers of Odin, a newly formed anti-immigration group, demonstrates in a city in eastern Finland. Fears are growing over the group's intentions as the country struggles to deal with the migration crisis

But as with other European countries, it is now struggling with a huge increase in asylum seekers and the authorities are wary of any anti-immigrant vigilantism.

A group of young men founded Soldiers of Odin, named after a Viking god, late last year in the northern town of Kemi, a border community which has become an entry point for migrants.

Since then the group has expanded to other towns, with members stating they want to serve as eyes and ears for the police who they say are struggling to fulfil their duties.

Members blame 'Islamist intruders' for what they believe is an increase in crime and they have carried placards at demonstrations with slogans such as 'Migrants not welcome'.

While most Finns disapprove of the group, its growth signals disquiet in a country strained by the cost of receiving the asylum seekers while mired in a three-year-old recession that has forced state spending and welfare cuts.

Like in nearby Germany, Finnish police have reported harassment of women by 'men with a foreign background' at New Year celebrations in Helsinki, as well as at some public events last autumn.

Police files show reported cases of sexual harassment in Finland almost doubled to 147 in the last four months of 2015 from 75 in the same period a year earlier. The figures give no ethnic breakdown of the alleged perpetrators.

However, the government has made clear there can be no place for vigilantes. 'As a matter of principle, police are responsible for law and order in the country,' Prime Minister Juha Sipila told public broadcaster YLE, responding to concerns about the group. 'Civilian patrols cannot assume the authority of the police.'

The group calling themselves the 'Soldiers of Odin' carry a placard during a demonstration in eastern Finland

But the police acknowledge patrolling alone is not a crime, saying: 'As long as the patrols only report possible incidents to police, they have the right to do so. [But] they should let the police do their job.'

Finland received about 32,000 asylum seekers last year, a leap from 3,600 in 2014.

In Kemi, the Soldiers of Odin patrol the streets daily, despite the temperatures sinking to -30C. The group has stated it operates in 23 towns, but police say the network operates in five.

'In our opinion, Islamist intruders cause insecurity and increase crime,' the group says on its website. One self-proclaimed member, aiming to recruit new members in the eastern town of Joensuu, said on Facebook the group is 'a patriotic organisation that fights for a white Finland'.

In Finland, no clashes have been reported between the Soldiers of Odin patrols and immigrants but police said they are keeping a close eye on the group. The Security Intelligence Service has said 'some patrol groups' seem to have links to extremist movements.

Some Soldiers of Odin members play down the group's motives, saying it aims to help people regardless of their skin colour.

The group has closed its website following reports on some members' criminal background. Members contacted by Reuters declined to comment.

Police are growing increasingly concerned about the anti-immigrant group's intentions as its members are pictured here during one of its foot patrols on the streets of Finnish cities

Police have admitted the group has a right to carry out patrols, which in itself is not a crime, but also said the vigilante group should leave fighting crime to the police

But one of the group's founders in Kemi, Mika Ranta, made clear immigration was the focus.

'We woke up to a situation where different cultures met. It caused fear and concern in the community,' he told a local newspaper in October. 'The biggest issue was when we learned from Facebook that new asylum seekers were hanging around primary schools, taking pictures of young girls.'

Vanska said some asylum seekers had been seen near schools with phones. But he added that these reports could be simple misunderstandings and there was no concrete evidence to support the accusations.

The coalition government - which includes The Finns, an anti-immigration party - has criticised the patrols.