Swiss intelligence has said the nation's first jihadist terror attack is a certainty as extremism spreads across Europe.

The country's defence minister warned it was not a matter of whether there would be an atrocity in Switzerland but, rather, when it will occur.

At the same time, the Swiss spy agency said the greatest threat on home soil came from so-called lone-wolf fanatics or small groups.

Swiss intelligence has said the nation's first jihadist terror attack is a certainty as extremism spreads across Europe (file picture)

Swiss Defence Minister Guy Parmelin was speaking today at a conference in Bern where the spy agency released its 2017 situation report.

It comes as Europe tries to come to terms with recent attacks in London and Paris linked to Islamist extremism.

'In Switzerland, the terrorist threat remains at a heightened level,' the Federal Intelligence Service (FIS) said in its annual assessment of risks faced by Switzerland.

'The most likely terrorist threat in Europe and thus also in Switzerland will continue to come from jihad-motivated terrorism,' it said. 'Further attacks must be expected.'

The FIS said the greatest danger was that individuals or small groups inspired by ISIS would carry out attacks in Switzerland or use it as a base to plot other attacks.

A man who killed at least 12 people when he drove a lorry into a crowded Berlin Christmas market (pictured) had also visited Switzerland and may also have obtained a gun there

FIS said it had identified more than 500 internet users with Swiss connections who were using social media to spread jihadist ideas.

Concerns about extremism and potential attacks led to Swiss voters last year backing a law extending the national spy service's authority to monitor internet traffic, deploy drones and hack foreign computer systems.

Switzerland has so far not been targeted directly in an Islamist attack, but it has had several links to attacks that elsewhere in Europe last year.

Two men who took hostages and killed a priest in northern France last July had travelled via airports in Geneva and Zurich.

Another man who killed at least 12 people when he drove a lorry into a crowded Berlin Christmas market had also visited Switzerland and may also have obtained a gun there.

'It is not yet clear whether these links to Switzerland played any role in the attack,' the FIS report said.

It comes as Europe tries to come to terms with recent attacks in London (pictured) and Paris linked to Islamist extremism

With no indication the fight against ISIS was coming to a close, there 'remains the considerable risk that the aggressive battle for the survival of the caliphate, fought using every means at their disposal, will increasingly be carried to Europe', the FIS report said.

Radicalised individuals returning from war zones were the most likely perpetrators, although the number of people leaving Switzerland to fight in Syria and Iraq had declined.

FIS director Markus Seiler said: 'With all the attacks we have seen, like in Sweden and France, we see from time to time there are links to Switzerland.

'Switzerland is not an island,' he added. 'Without being too alarmist, we cannot rule out that our country, being part of the West which jihadists consider as hostile to Islam, may one day be the target of a terror attack.'