Presiding Officer Ken Macintosh says there has been a serious incident at Westminster and it is in lockdown.

Mr Macintosh says security has been increased and he says the incident has affected this debate.

He says for that reason the debate will be suspended.

It will be resumed in a full and frank manner, but it the debate is suspended.

SNP MSP Alexander Burnett says "here we are again debating a constitutional question we have already answered."

Mr Burnett says the SNP did know about the possibility of Brexit.

The Tory MSP asks if the first minister will guarantee that Aberdeen and other areas will not be taken out of the UK against its will by Glasgow and Dundee. 

He says the collapse in oil revenues would have been "disastrous" for an independent Scotland had the vote been "yes" in 2014. 

Scotland's first minister has told the BBC she wants to find a referendum date that both sides can agree on.

Nicola Sturgeon said she was "up for continued discussion" with Theresa May on the matter.

The prime minister insisted this week that "now was not the time" to hold a second independence referendum.

And she indicated that the UK government would not give approval to the SNP's preferred timetable of between autumn 2018 and spring 2019.

Image source, AFP/Getty

heresa May has set out her desire to create a "more united" Britain, in a speech in Cardiff.

The prime minister told the Conservatives' spring conference that Britons are "at heart one people" be they Welsh, English, Scottish or from Northern Ireland.

It follows Nicola Sturgeon's  demands for a second independence referendum for Scotland.

Mrs May has already  rejected the call  from Scotland's first minister.

Douglas Fraser
Scotland business & economy editor

Image source, PA

The indyref2 campaign is already under way. Did it ever stop? Will it ever stop?

The arguments now are  political and constitutional . But what about the economic part of the debate? It mattered a lot last time. It will matter a lot if there's to be a next time.

Read more from Douglas Fraser here.

Labour MSP Jackie Baillie says it has only been two and half years since the last independence referendum and the promise was it would be once in a generation.

Ms Baillie say for the first minister a generation is five minutes. 

External Affairs Secretary Fiona Hyslop says the Scottish government proposals were for membership in the single market.

Ms Baillie says: "I know how the first minister operates and day after day there has been demand after demand, position change after position change and that is no way to negotiate."

She says she will vote against indyref2 tonight and she says the SNP ignore votes when the go against them and, like many opposition MSPs before her, she lists the votes the Scottish government have lost.

The Labour MSP says: "Democracy only happens when it is convenient for the SNP."

SNP MSP George Adam says this is not just a debate about what is right for Scotland going forward but the democratic right of the Scottish people.

Mr Adam says he is an advocate for choice and the people must be allowed to decide and enact the power they want to see.

"Change is now inevitable and it is up to the people of Scotland what change they want to see," he says.

The SNP MSP says the Scottish government only discovered Article 50 would be triggered via the news.

He says time and again the Scottish government have sought compromise which would see Scotland remain in the single market. 

"Now is the time to give the people of Scotland the chance to escape a hard-Brexit," he says.

Image source, bbc

Deputy Presiding Officer Linda Fabiani says a suspension has been considered but the decision has been taken to "carry on with business as usual".

Image source, bbc

Scottish Conservative MSP Murdo Fraser says many members are distracted by the news for Westminster.

Mr Fraserasks if it would be appropriate for this debate to be suspended.

Tory MSP Annie Wells says she did not expect that only 917 days since the last vote that she would be back here debating another independence referendum.

Ms Wells says "we were aware that there was going to be an EU referendum as was Nicola Sturgeon." 

The Tory MSP says poll after poll has shown no shift in public opinion towards independence. 

"People are starting to get tired of the SNP," she says, adding that the Scottish government must get back to its day job. 

Ms Wells says Scottish Greens co-convener Patrick Harvie previously said that another referendum should only be called if it is the will of the people. 

SNP MSP Joan McAlpine says "only by working together with our European allies can we be truly independent". 

Ms McAlpine says the EU referendum result was challenging but it is the aftermath that has been most revealing.

The SNP MSP says Scotland's Place in Europe is a "serious and credible compromise". 

Ms McAlpine says that responses on Brexit decisions should have been communicated directly to the Scottish government and not received through the media. 

Image source, bbc

Deputy Presiding Officer  Linda Fabiani says there are reports of an incident at Westminster and details are still  emerging.

Ms Fabiani says security is under review at Holyrood and members will be updated when a clearer picture emerges.