Sinn Fein's Deputy First Minister Martin McGuinness said all threats against democratically elected representatives should be withdrawn immediately.
There is no justification for this type of intimidation from any grouping or organisation
More top news
Police have warned the drug, known locally as "pink champagne", could be deadly.
The author said "It's been wonderful" as fans mark two decades since the children's books opened up a world of magic to millions.
There was something very striking about the pact, which implies the new agreement could remain in place even if the prime minister does not.