Police in the North are still questioning four people in connection with a disturbance in Belfast ahead of Northern Ireland's World Cup qualifier match with Poland.
Fireworks, bricks and bottles were thrown at police officers as rival football fans clashed before and after last night's game at Windsor Park.
Play was briefly halted when an object thrown from the crowd hit a linesman.
After the match, police in riot gear were pelted with fireworks, bricks and bottles - eleven of them were injured.
A number of homes in the area were attacked in what police said were racially motivated incidents.
Earlier in the day, nine people were arrested following trouble at a city centre pub.
Five of them have been released without charge.
The PSNI has condemned the violence and said CCTV footage is being examined to identify those responsible.