Security for the COP26 climate summit in Glasgow this year could cost "several hundred million pounds", a new report suggests.

Papers to go before the Scottish Police Authority (SPA) board this week have outlined the potential cost of the event, which will bring heads of state from around the world to Scotland in November.

The papers say "dialogue remains ongoing" with the UK Government as to who will foot the bill for security.

The Scottish Government has previously said Westminster should pick up the tab, with Justice Secretary Humza Yousaf claiming the UK Government should fund the entire security provision.

It will be the largest summit the UK has held, with up to 200 world leaders expected for the final weekend of talks and around 30,000 delegates in total.

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According to the papers, "detailed financial planning" is underway, with discussions between the police authority and the Cabinet Office in Westminster ongoing.

In September - when Glasgow was announced as the host city for the summit - Police Scotland said the costs to the force would be in the "tens of millions", while October estimates by the Justice Secretary placed the cost at £100 million.

It is not clear what has caused the increase in expected costs - but the new estimate has used other events, such as the Nato Summit in Wales in 2014, as a baseline for costings.

The report said: "Taking into consideration the planning assumptions and based on previous major summits/conferences (e.g. Nato Summit Wales
2014), the initial costings demonstrate that the event will cost potentially several hundred million pounds.

"Detailed financial planning is being developed and dialogue remains ongoing with the Cabinet Office relative to the cost recovery model that will be utilised."

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The report also outlines plans for police officers from other forces to be sent to Scotland to aid the force in what is described as "undoubtedly the largest mass mobilisation of police officers in the UK", adding it will present "extensive logistical challenges".

The Scottish Event Campus will play host to the event, being handed over to the United Nations for the summit's entirety.

A Scottish Government spokeswoman said: "Scotland looks forward to welcoming the United Nations delegates and participants from around the world later this year. Scotland is recognised internationally for its strong track record at hosting major international events and we are working collaboratively with the UK Government, Glasgow City Council and other partners to ensure the conference is a success.

"While the UK Government has committed to cover core costs, Scottish ministers expect that all costs associated with COP26 will be borne by the UK Government. This includes funding for police, fire and ambulance services to both prepare for and deliver a safe, secure and successful event. We continue to push the UK Government on the lack of clarity on this key issue."