People light candles outside Kronan school in Trollhattan, Sweden. A masked swordsman who killed a teaching assistant and a boy and wounded two others, all with immigrant backgrounds, was driven by racist motives, Swedish police say. Photo: Reuters

A masked swordsman who killed a teaching assistant and a boy and wounded two others sought out his victims, all with immigrant backgrounds, by skin colour in an attack that has fuelled fears that a big refugee influx is polarising Swedish public opinion.

The 21-year-old assailant strode through a school in Trollhattan on Thursday, an industrial town in western Sweden with a large immigrant population, stabbing his victims with the sword before being shot dead by police. Security footage showed the killer marching through school corridors and stopping to talk to light-skinned students, police said.

“Everything points to this being a hate crime,” lead investigator Thord Haraldsson told a news conference. “He selected his victims and attacked the dark-skinned ones and left the light-skinned ones alone." Interior Minister Anders Ygeman said record numbers of refugees had fuelled racism among a small segment of society.

“We will have to ask ourselves several questions about how society is developing, about polarisation, and mobilise all good forces against this racist violence,” Mr Ygeman told TV4. The killings happened on the same day that the government announced up to 190,000 refugees, a record number, could arrive in Sweden this year.

We will have to ask ourselves questions about how society is developing

The government and opposition agreed yesterday to restrict Sweden’s generous immigration policies, worried that its resources have been stretched to their limit with tents being prepared to shelter thousands of new arrivals. Mr Ygeman defended the government’s liberal asylum-seeking policies, under which Sweden had accepted more refugees per capita than any other European country in recent years.

“You can’t blame asylum policy because we have a madman who murders children,” Mr Ygeman said. Swedish media said one of the dead, a 17-year-old pupil at the school, had come to Sweden from Somalia three years ago. A 15-year-old, recovering in hospital from stab wounds, had recently arrived from Syria. Police said they had found a “a sort of suicide note” which clearly pointed to racist motives and showed the assailant had acted alone.

In a photo taken after the killer had stabbed at least one person, he posed in a corridor with pupils who thought his cape, mask and World War Two-type helmet were part of a Halloween prank.

The suspected killer's social media accounts showed likes for pro-Nazi video clips and an anti-immigration campaignt.