Finland's government has condemned a protest in which demonstrators - including one reportedly dressed in a Ku Klux Klan outfit - attacked buses transporting asylum seekers.
TV pictures showed buses being pelted with fireworks near the city of Lahti.
No one is believed to have been hurt.
European Commission Vice-President Frans Timmermans has warned of a "surge" in far-right extremism if Europe fails to tackle the migrant crisis.
Young children were among those on the two coaches targeted late Thursday as they arrived at a converted army barracks in Hennala, near the southern city of Lahti.
Finish media said between 40 and 50 protesters - some with flaming torches - confronted up to 50 migrants. They also threw stones at Red Cross workers.
State broadcaster YLE published a photograph of one of the demonstrators wearing a white Ku Klux Klan outfit and waving a Finnish flag.
Prime Minister Juha Sipila condemned the attack in a joint statement released (in Finnish) on Friday with his foreign and finance ministers.
"Finland's government condemns last night's racist protests against the asylum seekers who have come to the country," it said.
"Violence and threatening behaviour is always indefensible."
More than 11,000 asylum seekers are believed to have arrived in the Nordic country so far this year, compared to 3,651 last year.
In its statement, the government insisted Finland was "an international, open and tolerant country" where the large majority of people accepted immigrants.
PM Sipila says Finland, a country of 5.5m people, should set an example to the rest of Europe on migration.
However, his coalition partners are the anti-immigration Finns Party, whose leader, Timo Soini, is foreign minister and deputy prime minister. Some Finns Party MPs have hit out at what one called a "nightmare of multiculturalism".
On Saturday more than 500 people formed a symbolic "human wall" in the northern Finish border town of Tornio to protest against the arrival of hundreds of migrants via Sweden.
Thursday's unrest came after EU leaders met for an emergency summit on the migration crisis and interior ministers voted to resettle about 120,000 migrants across Europe.
Under the quota plan, Finland would have to accept another 1,286 asylum seekers from 66,000 who have already arrived in Italy and Greece.
As debate over the proposals exposed splits in the EU, Mr Timmermans warned that if a solution was not found, far-right political groups might gain ground.
"If we are not able to find sustainable solutions, you will see a surge of the extreme right across the European continent", he told BBC Radio 4's Today programme.