I would be travelling in Norway, Sweden, Denmark and Spain for about 4 weeks. I need to get a mobile phone but need free incoming. I already have an unlocked GSM phone so just need the sim card.

Is there one company that provides this for multiple countries or would I need to buy a sim card in each country I visit ?

Is it easy to get individual sim cards from these countries and would they be available at airports ?Any idea on the requirements especially since I'm not a EU resident ? Any details on this would be veey helpful.

Thanks

Can't speak for Norway or Sweden, but I don't believe you can get a prepaid SIM card in Denmark without a CPR number (basically a Social Security number). Certainly, there is nowhere in the CPH airport to get one.

In Spain all you do is show your passport.
You can purchase a SIM card to keep your number the same throughout your trip, but you will pay roaming charges when used in a different country. However some good news here is that the EU has capped those charges so they are reasonable now.
The alternative is to purchse one in each country

<i>In Spain all you do is show your passport.</i>

That is the way it is in most civilized countries. I have, however, been specifically told that Denmark does not allow this. Prior to moving to Denmark, I asked my relocation agent specifically about buying a prepaid SIM card to use while awaiting my CPR card. I was told that you couldn't buy them without a CPR card.

Even if my relocation agent was wrong, it is certainly the case that they are not as common in Denmark as in other countries. You can't just buy them at the grocery store, for example, and would need to go to a cell phone store or other authorized agent, like an electronics store.

I remember reading that some other country does this. Japan, maybe? The intent, I believe, is to reduce fraud and criminal activity.

Telestial.com sells passport SIM cards that are good throughout Europe and many other countries. You get a UK number and now I think the product has a US number as well. Check their website and current offerings to see if their SIM products, pricing, etc. fits your needs.

TravelSIM http://www.travelsim.com/content/eng/13/ may be a solution.