Police have been called to Limavady Borough Council's offices after a meeting had to be abandoned.
Officers were called to attend to reports of a disturbance and assault at the offices on Connell Street at about 2200 GMT on Tuesday.
It is understood a group of up to 50 protestors turned up for the meeting, where the issue of neutral spaces in council areas was being discussed.
Two Sinn Fein councillors said they were abused as they left the building.
The councillors, Anne Brolly and Marion Donaghy, said they were confronted by a crowd outside the council offices.
"There was a particularly nasty mood among the young men who were there," Ms Brolly said.
"They spat on us and they were very vitriolic and made obscene comments and threats to us.
"When we got into the car one man threw a Union Jack over it and shouted obscenities at us."
Limavady mayor Edwin Stevenson said he had no hesitation in condemning what had happened, but said it was too early to discuss the removal of emblems.
"If Sinn Fein had really been interested in accepting everyone's culture, I think this would be much better left for a future date," he said.