UPDATED 12.38pm: The Prime Minister's not convinced bombing Syria is the best way to deal with Islamic State.

Global efforts to combat the Islamic State group have gathered pace with with France and Russia ramping up air strikes in wake of the Paris attacks and the bringing down of a Russian airliner.

LISTEN: Prime Minister John Key speaks with Mike Hosking

British Prime Minister David Cameron has also pledging solidarity during a visit to France and Russian leader Vladimir Putin meeting his allies in Iran.

French President Francois Hollande is set to meet all five permanent members of the UN Security Council, and the United States trying to rally support for a ceasefire in Syria.

US Secretary of State John Kerry is in Abu Dhabi hoping to forge a coalition of Syrian opposition groups for peace talks.

John Key acknowledged eradicating Islamic State off the face of the earth would be great, but he doesn't think air strikes will stop people joining the terror group.

"Part of this is ultimately diplomacy. It is finding a place in Iraq for Sunnis and Shia and the Kurds can live alongside each other."

He said the main problem with Islamic State is that it's a decentralized group that uses the internet to recruit followers.

"It is so much easier to identify the problem and to say it is bad, wrong and should be dealt with, and so much harder to actually physically do it."

Criminal cases against Islamic State suspects must be water tight

The Prime Minister has also signaled criminal cases will have to be water tight if people with suspected links to Islamic State are to be prosecuted.

John Key said among the 40 people currently being monitored by security agencies, a small number are under 24-hour surveillance.

He's indicated some are on the periphery of Islamic State and said if they could prosecute someone they would.

"The issue always is is that people can go to court and we'll make a case that we've somehow misinterpreted what they're doing so that the authorities will act but they'll only act at a time when they're only absolutely sure that they can get a successful prosecution."

He said authorities aren't sure they have the ability to put Kiwis with ties to Islamic State in jail for extended sentences.

"You could probably get the prosecuted under some breech of the law, but it might be for not long enough relative to what we think so it's better for us to carry on doing what we're doing."