Scotland’s devolved parliament suspended a planned vote on Wednesday to give its government a mandate to seek a new independence referendum after an attack on Britain’s Houses of Parliament in London.
The police said they were treating the attack as a terrorist incident, after a policeman was stabbed, an assailant shot and several people were injured.
No date for the debate to resume was given for now.
The Scottish parliament issued a statement saying it would increase security measures, although no specific threat to Scotland had been detected.
London’s permission for a new Scottish referendum is needed because any legally binding vote on UK constitutional matters has to be authorised by the UK parliament.
Prime Minister Theresa May has not completely ruled out another Scottish independence vote but has vowed to fight for what she has called the “precious union” of the UK.
First Minister Nicola Sturgeon, who argues that Scotland’s vote to keep its EU membership in last June’s referendum has been ignored in May’s Brexit arrangements so far.
He is seeking authority for a second referendum from the Scottish parliament, to be held in late 2018 or early 2019.