Local units of the two main loyalist terror organisations in Northern Ireland were behind events that have seen 40 Polish migrant workers flee in recent weeks, the Guardian has learned.

Members of the Ulster Volunteer Force and the Ulster Defence Association in south Belfast organised the intimidation of the Poles over the past fortnight, security sources in the city said.

The attacks on Polish homes in south Belfast were believed to be in response to an outbreak of hooliganism by soccer fans from Poland during last month's World Cup qualifier at Windsor Park.

Before the crucial Northern Ireland versus Poland match in Belfast on March 28, a group of Polish hooligans smashed up pubs and attacked local fans.

The Police Service of Northern Ireland released figures yesterday revealing that in the aftermath of the soccer violence at least 40 Polish nationals had to flee their homes in the south of the city.

One senior security source said last night that a series of revenge attacks had been co-ordinated by local UDA and UVF units.

"The attacks were not carried out officially in the name of either organisation but all the intelligence points to the involvement of loyalists who are of course meant to be on ceasefire and not engaged in paramilitary activity," he said.

The nationalist SDLP and the Green party in Northern Ireland condemned those behind the assaults.