A spokesman for Northern Constabulary has said that the three people airlifted to hospital are "believed to be in a serious condition".
He added that two groups of six people had been in the area at the time of the avalanche, and have now been "walked off" the hill.
More top news
The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.
As temperatures climb through the day, the warmest spots are likely to be across western parts of Northern Ireland and western Scotland.
Boris Johnson and Amber Rudd have both criticised social media giants for failing to detect and remove extremist material online.