Poland's defence minister has told Sky News his country is facing its greatest security crisis since the end of the Cold War.

Speaking from the ministry of defence in Warsaw, Tomasz ‎Siemoniak said they must be prepared for the situation to deteriorate further, and for Russia to expand its ambitions beyond the annexation of Crimea.

"We can see that Russia is going in the direction of restoring the influence it had at the time of the Soviet Union," Mr Siemoniak said.

"If that is the case then the situation is not over by any means with Crimea and it will move on to the territories of other countries, that will either be targeted by aggression or by some other measures taken by the Russian federation, so we have to be ready.‎"

Poland has increased defence spending by 18% to meet NATO's target of 2% of GDP, as well as expanding the size of its reserves.

The country is undertaking an ambitious rearmament programme, attempting to overhaul its dependence on ageing Soviet-era equipment by 2022.

The defence ministry is also drawing up plans to help train and integrate civilian paramilitary groups, which could be mobilised in the event of war.

Volunteer territorial defence organisations have reported a surge in new members since the start of the conflict in neighbouring Ukraine.

"Ukraine is our neighbour," 22-year-old Karol explained. "I think the Polish people need to feel more confident."

Huberet, a middle-aged architect from Warsaw, who used to take part in Napoleonic battle re-enactments, told us: "This is the history, but in the situation where this Ukrainian conflict is actually 1,000km (621 miles) from us, I made a decision that I have to learn how to fight in these times.

"So I have to switch from the horses and sword-fighting to things that are useful in this army today."

In a forest outside Gdansk in northern Poland, we met members of the Strzelec‎, or riflemen, one of the country's oldest paramilitary groups.

They too have seen an influx of applications to join.

‎We filmed an abseiling training session from a watchtower looking out towards the Baltic Sea.

Poland borders Russian military enclave Kaliningrad, 93 miles (150 kilometres) to the east.

A 26-year-old paramedic who gave his name as Kuba said: "Everybody in here shoots by AK-47 and Glock pistol.

"We will teach everybody how to shoot, how to rescue people, how to camouflage, how to use radios, basic knowledge in the field."

Logically, an attack on Poland - a permanent member of NATO - remains extremely unlikely, but it does not feel quite as unthinkable to people here.

Asked whether he really felt war was a possibility, whether the threat was real, Kuba replied: "I think everybody who has a clear mind in Europe knows the war is a true possibility, especially in Poland."

‎Another man, abseiling head-first past our camera, shouted: "History shows us what our neighbours can do."