There are concerns western Governments are playing into the hands of terrorists, by reinforcing a climate of fear and anxiety.

Terror threats in Munich, Moscow, Brussels and New York had authorities on high alert over New Year's Eve, and one terror expert says that anxiety is likely to linger.

Train stations were evacuated in Moscow and 6000 extra police patrolled Times Square - just two examples of how western authorities are responding to perceived terror threats.

Professor Richard Jackson of the National Centre for Peace and Conflict Studies said terrorists need only make a phone call and say they've planted a bomb for everyone to go crazy - regardless of whether it's true.

He said it's a trap that governments find themselves in and says by perhaps overreacting to every terror attack, they make it easier for terrorists to disrupt society.

"These groups tend to be able to launch these kinds of attacks ever year, or every 2 years even, they certainly can't do it every week, and they certainly can't do it every month - they just don't have that kind of capacity," he said.

But Professor Jackson expects Islamic State to try and increase its attacks, after the upsurge in Europe coalition attacks against it.

He said the actions of European authorities play into a series of new laws being brought in covering surveillance, greater powers for security services, and ramping up the war against ISIS in Iraq and Syria.

Professor Jackson said if you can keep the public in a state of anxiety - through terror alerts and increased police on the streets - it makes it easier to get those measures passed into law.