Switzerland tops a global ranking of happiness, closely followed by Iceland, Denmark, Norway and Canada in a comprehensive study unveiled by academics in New York on Thursday.

The 2015 World Happiness Report is the third annual report that seeks to quantify and explain happiness in 158 countries as a means of influencing government policy across the planet.

Iceland has closed down a website believed to be used by the jihadist organization Islamic State, according to the authority responsible for the country's Internet domain name ".is".

Internet in Iceland Inc, or ISNIC, said in a statement late Sunday that it had "suspended domains that were used for the website of a known terrorist organization".

China refuses to clarify the status of its ambassador to Iceland, who left the country mysteriously in January, the Icelandic foreign ministry said Wednesday, after a news report that he has been arrested for spying for Japan.

The envoy, Ma Jisheng, has not been replaced, and Reykjavik has been informed only that he was unable to return for "personal reasons", foreign ministry spokeswoman Urdur Gunnarsdottir told Agence France-Presse.

Iceland reopened the airspace over the Bardarbunga volcano system Friday afternoon, lowering a red alert to aviation declared earlier following an overnight eruption.

The Icelandic Meteorological Office, charged with monitoring volcanic activity, said it had lowered the alert level to orange, meaning flights could pass over the area.

Iceland lowered its alert over the nation's largest volcanic system to orange on Sunday after keeping it for one day at the maximum level amid fears of an imminent eruption.

A major explosion at the Bardarbunga volcano, located under a glacier, could signal a replay of the global travel chaos triggered when another Icelandic peak blew four years ago, creating a massive ash cloud across Europe.

Iceland raised its alert over the nation's largest volcanic system to red on Saturday, banning all air traffic in the area, as experts deemed imminent the risk for an eruption.

Tourists and hikers were evacuated Wednesday near a massive rumbling volcano in Iceland as the threat of eruption raised fears of a replay of the air traffic chaos caused when another peak blew four years ago.

Iceland's Civil Protection Authority told public broadcaster RUV that it had finished the evacuation from around the Bardarbunga volcano but that further air patrols would be carried out to ensure no-one remained.

Iceland has warned that its largest volcano is in danger of erupting, four years after millions of air travelers were grounded by a huge ash cloud from another peak.

Scientists believe the ash from an eruption at Bardarbunga could disrupt transatlantic and northern European air traffic, with floods of melting ice likely to cause serious damage to the country's infrastructure.

Iceland has postponed plans to withdraw its application for European Union membership, the government said Monday.

The island nation's euroskeptic center-right government announced on February 21 a draft bill to retract Iceland's 2010 EU membership application without holding a referendum.

Iceland's currency, the krona, was declared "dead" five years ago but it survived and with European Union membership ruled out for the forseeable future it is likely to limp on.

"The krona is dead. We need a new currency. The only serious option is the euro," an Icelandic official told the British newspaper The Guardian in January 2009.