The Democratic Ulster Party's Paul Givan described the attack as despicable. He said protests should be stopped if they could not be peaceful.
It is vital that those who continue to have protests, if they cannot guarantee that there will be no violence; that there will be no blocking of roads and no disruption to people's way of life, that they do not go out onto the streets and they should desist from that activity.
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A wet, wintry night in places with rain and hill snow slow to move away from southern Scotland and northern England.
The Westminster terror attack dominates the front pages of Thursday's newspapers.
A timeline of exactly what happened.