* Greenland publishes Cairn Energy's oil spill plan
* Acts to calm environmental fears over Arctic exploration
* Says authorities can take action 5 km around rig
COPENHAGEN, Aug 16 (Reuters) - Greenland has published British explorer Cairn Energy's oil spill response plan in a bid to calm fears about Arctic exploration after environmental group Greenpeace demanded that it be made public.
It also said it had new options to act against any unlawful attempts by protesters to interfere with oil rigs.
Greenpeace, which has tried to disrupt drilling off Greenland, argues that cleaning up a spill in the Arctic waters there would be extremely difficult.
Greenland's government had initially withheld the oil spill contingency plan drawn up by Cairn because it feared activists could launch more actions against rigs if it were published.
Greenland, a semi-autonomous part of the kingdom of Denmark, said the Danish foreign ministry had determined that under the U.N. Convention on the Law of the Sea the Greenland authorities can take action within a radius of 5 km from a safety zone around oil rigs.
"These new options available will make it easier for the authorities to take measures in relation to unlawful actions against the safety measures of the drilling rigs," the Greenland government said in a statement on its website.
"This means that the risk of accidents that may cause loss of lives and result in pollution of the environment can be reduced," it said.
The officials listed five incidents in which they said Greenpeace activists unlawfully disturbed drilling off Greenland between August 2010 and June this year, including boarding the Leiv Eriksson rig leased to Cairn Energy.
Edinburgh-based Cairn Energy last year became the first company to drill for oil and gas off Greenland in a decade, but so far it has not found commercial amounts.
Greenland is seen a new Arctic frontier for oil and petroleum exploration, and a 2008 assessment by the U.S. Geological Survey said its waters could hold huge resources.
Environmental groups say the Arctic is particularly vulnerable to oil spills, and fears have grown after the blow-out of BP's Macondo well in the Gulf of Mexico last year.
The Greenland government said Cairn Energy's contingency plan was prepared with help from Oil Spill Response Limited (OSRL), which it called "one of the world's leading oil spill response companies" and Cairn's sub-supplier of oil spill response equipment and services.
"Cairn's and OSRL's response services are based on the ability to handle very large oil spills," the government said.
In case of minor (Tier 1) oil spills, OSRL has installed equipment on the drilling units or the vessels around them that can solve the task, it said.
In case of medium (Tier 2) spills, OSRL has placed equipment in Aasiaat, Kangerlussuaq and Nuuk to handle such task, it said.
In case of major (Tier 3) spills, equipment from OSRL will be mobilised from the port in Southampton in Britain, and chemicals, equipment and staff will be transported to Greenland by air freighters, it said.
"It has been documented that the worst possible response time for Tier 3 equipment to a drilling location is 52 hours," the Greenland authorities said.
If there were to be an oil spill requiring even more resources, OSRL collaborates with six large oil spill response organisations that are part of the so-called Global Response Network (GRN), the authorities said.
Abatement strategies would consist of mechanical recovery of oil, in-situ burning on the surface or chemical dispersion.
The government said drilling in icy conditions is banned.
"First and foremost it is important to establish that drilling is not permitted in the sea ice season in Greenland," it said.
"The drilling of wells in Greenland must stop at least two months before the sea freezes up so that there is time, if necessary, to drill a relief well and to abate and clean up after a potential oil spill," it added.
If oil were left in the sea when ice began to form, the cleanup would continue for as long as possible and resume once the ice melted, it said.
"In that respect an oil spill in Greenland does not differ from all other places in the world, including the production that takes place in the Arctic areas, for example north of Alaska and north of Russia and Norway," it said.
Greenpeace International said on its website it would conduct an analysis of the plan and post it on the site soon.
"At a glance, we see very little to allay the concerns of experts and analysts who believe a BP-style blow-out would wreck the fragile Arctic environment and its fisheries," Greenpeace said.
"We've also seen nothing to cause us to disagree with the claims of the UK government which, in private documents, said an Arctic spill would be 'near impossible' to clean up," it added. (Reporting by John Acher; Editing by Anthony Barker)