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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Rain will spread eastwards across southern areas tonight. Clear and frosty in the north.
Political leaders will go head-to-head at ITV's studios in MediaCityUK in Salford, ITV has confirmed, as the set for the event is unveiled.
More than 100 people claiming to represent working people across Britain have signed a letter backing Labour in the general election.