By Johan Ahlander and Simon Johnson
STOCKHOLM (Reuters) - 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 said on Friday, fuelling concerns that refugee numbers were polarizing public opinion in the country.
The 21-year old assailant walked through a school in Trollhattan, an industrial town in western Sweden with a large immigrant population, stabbing the assistant and boy to death with a sword before being shot dead by police.
Police said all the victims were from immigrant backgrounds, and Interior Minister Anders Ygeman said record numbers of refugees had fueled racism among a small segment of society.
The attack came on the same day that the government announced up to 190,000 refugees could arrive in Sweden this year, a record number that has strained resources and seen several arson attacks on asylum seeker centers.
"We will have to ask ourselves several questions about how society is developing, about polarization and mobilize all good forces against this racist violence," Ygeman told TV4. "Of course there is a connection in the sense of the social climate."
But he defended the center-left's liberal asylum-seeking policies that have seen Sweden accept more refugees per capita than any other European country in recent years. Over the decades, Sweden has welcomed refugees ranging from Vietnam war draft dodgers in the 1960s to Gulf War refugees in the 1990s.
"You can't blame asylum policy because we have a madman who murders children," 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.
"Three factors point to the hate crime motive: the way he acted and how he was dressed during the attack at the site, and also findings at the flat where he lived," Trollhattan police spokesman Stefan Gustafsson told Reuters.
In a photo taken after the killer had stabbed at least one person, he posed in a school corridor with pupils who thought his cape, mask and WWII-type helmet were part of a Halloween prank. Moments later he stabbed a teacher who approached him.
"Then he chased us through the school, we were terrified," one girl told Aftonbladet.
The suspected killer's social media accounts showed likes for pro-Nazi video clips as well as an anti-immigration campaign, according to local media.
"We have never felt afraid in Sweden," daily Aftonbladet quoted the mother of the injured boy saying.
School attacks are almost unheard of in Sweden - the last incident was near the city of Gothenburg in 1961 when one student was shot dead and six others were injured - and violent crime in general is rare.
Polls show most Swedes welcome refugees. But with up to 190,000 asylum seekers expected to arrive this year, tensions have been rising.
A number of asylum centers have been attacked in the past week. Police were forced to beef up security at centers in August after the murder of a Swedish man and a woman by a refugee at an IKEA store in the city of Vasteras. The refugee had been denied asylum shortly before the attack.
The anti-immigrant Sweden Democrats party has seen its popularity soar with polls showing it would get around 20 percent of the vote now, up from around 13 percent in a general election last year.
The party plans an advertising campaign in foreign media aiming to warn off asylum seekers.
(Additional reporting by Niklas Pollard and Bjorn Rundstrom; Editing by Alistair Scrutton and Hugh Lawson)