HOLYROOD bosses postponed their debate on another Scottish independence referendum yesterday as a mark of respect for the tragic events at their “sister Parliament”.

First reports of the attack in Westminster started appearing just minutes after Fiona Hyslop started the historic debate on the Section 30 order.

There was seemingly fierce discussion between parliament officials over what to do, with most agreeing it was best to carry on with “business as usual”.

As the extent of the attack emerged, a number of MSPs, including Ruth Davidson and Kezia Dugdale, took to social media to vent their frustration at this decision.

“Surely Scottish Parliament business should be suspended out of respect” Dugdale tweeted.

Not long after the debate started First Minister Nicola Sturgeon, Justice Secretary Michael Matheson, and Presiding Officer Ken Macintosh had all left their seats, and were being briefed on the unfolding situation Tory MSP Murdo Fraser raised a point of order asking for proceedings to come to a halt, but deputy presiding officer Linda Fabiani said the parliamentary session would continue.

Some politicians walked out. Fin Carson tweeted: “I have left chamber. I can’t understand how this debate can go on. At least a suspension would have shown some respect.”

Many others from all benches were on phones, looking at Twitter and checking on colleagues and friends in and around Westminster.

The parliament’s chief executive, Paul Grice, issued a security warning to all Holyrood’s staff, MSPs and journalists saying that security had been increased “with immediate effect”.

He wrote: “We are aware of a developing situation at Westminster this afternoon and are monitoring matters very closely.

“While there is no intelligence to suggest there is a specific threat to Scotland, Edinburgh or Holyrood we have increased security with immediate effect at the Scottish parliament as a precaution. In the meantime, we would ask all building users to be vigilant while going about business and also when leaving or coming to parliament.”

By 4pm, and an hour and 20 minutes into the debate, Presiding Officer Ken Macintosh called a halt to proceedings.

The Presiding Officer said: “The fact that our sister parliament has had a serious incident is affecting this particular debate, and is affecting the contribution of members. And so it is for that reason we are deciding to suspend the sitting.

“We will resume this debate and we will be able to do so in a full and frank manner, but I think to continue at the moment would not allow members to make their contributions in the manner they wish to.”

In a statement issued later, Macintosh said that “as the true seriousness of the incident emerged, and as an expression of our support for our sister Parliament, parliamentary business at Holyrood was suspended this afternoon for the remainder of the day.

“No matter how significant our debate might be, to have continued further would not have been appropriate.”

SNP Brexit minister Mike Russell tweeted: “Right to suspend @scotparl for many reasons not least in solidarity & sympathy.”

Not all MSPs agreed with the decision. Liberal Democrat MSP Mike Rumbles said it was a “mistake”, telling BBC Scotland: “We should not be giving in to terrorism, and I believe we’ve done that”.

The First Minister said Scottish ministers had been liaising with Police Scotland, with officials holding a Scottish government resilience (SGoRR) meeting with the force “to ensure that any potential implications for Scotland are considered”.

Sturgeon added that she fully supported the suspension of the debate, but stressed the decision “was not because of any specific threat to the parliament or to Scotland”.

After Parliament had been suspended, Fabiani addressed head on criticisms that it had been the SNP who had kept proceedings going, despite the protests of others.

“For info — decision to suspend is a decision of the Parliament through the Business Bureau — all parties, not just one. As it should be,” she tweeted.

Police vehicles were seen outside the parliament building, with a spokesman for Police Scotland saying the force was “liaising with colleagues in London and will ensure appropriate safety and security plans are in place based upon what we know”.

There are only two sitting days at Holyrood before Theresa May triggers Article 50, the formal process for leaving the EU, and Holyrood’s parties will have to try and move other business around to fit in the debate and the vote on requesting a Section 30 order from Westminster.