The Islamic State is preparing for a 'final battle' with the West, a terror expert has claimed.

As air strikes mount in the terror group's heartland, jihadists will attempt to increase attacks in response, geopolitical analyst Dr Theodore Kasik said.

His claim comes days after ISIS leader Abu Bakr al-Baghdadi pledged to attack the West, and as cities across the world tighten security at New Year's Eve celebrations.

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Threat: Islamic State leader Abu Bakr al-Baghdadi pledged to attack the West in a recorded message

Claims: Islamic State terrorists will attempt to increase attacks, geopolitical analyst Dr Theodore Kasik said

Dr Kasik told The Sun, the leader's message released on Boxing Day was a call to arms and that Baghdadi’s promise of more terror attacks and a 'final battle' was a tactical change that was enforced by the recent air strikes.

'ISIS is getting hammered in the Levant relentlessly by a combination of the US-led Operation Inherent Resolve and Russian strikes,' he said.

'To boot, former stronghold Ramadi was recaptured by Iraqi security forces, with Mosul next on the Iraqi list to roll back ISIS.'

In London, every firearms officer will be on duty for the New Year celebrations tonight in an unprecedented security operation.

Scotland Yard has cancelled leave for more than 2,000 armed police – the first time it has taken such a step.

It comes amid intelligence warnings that Islamist fanatics may be planning a terror attack in a European city – although there is no specific information to suggest London is the target.

Security concerns: Every firearms officer in London will be on duty for New Year celebrations. There was a noticeable armed presence on the streets of the capital yesterday, including outside the Houses of Parliament

Terror fears: Officers carry out searches as Brussels remains on high alert over a possible terror threat

Last night, officials in Brussels announced that the city's New Year celebrations had been cancelled as the Belgian capital remains on high alert over a Paris-style terror attack.

Mayor Yvan Mayeur said the decision had been made because officials could not guarantee being able to 'check' all attendees.

In 2014, some 100,000 people turned out to enjoy the festivities and fireworks display at the Place de Brouckere.

Austrian police have stepped up security in Vienna and other cities after receiving a warning of possible attacks.

Moscow’s Red Square, traditionally a place where Russians gather to ring in the New Year, will be closed to revellers amid mounting security concerns.