The police are examining possible racial motives for separate attacks in Counties Londonderry and Antrim.
A man, thought to be Lithuanian, was injured in an assault at a house in Riverside South, Castledawson, on Sunday. The house was also set on fire.
One man was arrested. Meanwhile, police are investigating an arson attack in Carrickfergus at 0800 BST on Sunday.
The back of the house at Burleigh Drive was extensively damaged after an oil tank caught fire.
It is believed the people who live in the house are Polish nationals. No-one was injured in the incident.
Police have appealed for anyone with information about either incident to contact them.
The latest two attacks come a day after what was believed to have been a racist attack on a Latvian man in Lisburn, County Antrim.
The victim sustained head injuries and a serious eye injury in the assault on the Moira Road, Lisburn.
A police spokesperson said the man was set upon by two men with baseball bats and sticks.
One man has been arrested.