New prime minister Sigurdur Ingi Johannsson yesterday replaced Sigmundur David Gunnlaugsson, who quit on Tuesday amid mass protests over a hidden offshore account revealed in the "Panama Papers" leak of millions of financial records.
Johannsson, a 53-year-old former veterinarian, has already announced new legislative elections will be held in "the autumn", about six months ahead of the scheduled April 2017 vote.
But protesters have demonstrated outside parliament for three days in succession, throwing eggs and yoghurt at the building.
Johannsson was sworn in by President Olafur Ragnar Grimsson at the presidential residence in Reykjavik.
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"You will see the difference," he promised later, but if he was expecting any political honeymoon he was quickly disappointed.
"Kick out the crooks," demonstrators yelled outside the presidency, as he assumed his tricky premiership.
Earlier, as Gunnlaugsson handed in his resignation to the president, he was met by angry protesters who brandished red cards at him and chanting: "Elections immediately, we want to vote!"
Formed in 2012 and campaigning for more transparency in politics, Internet freedoms and copyright reform, the Pirate Party is now credited with a whopping 43 per cent of voter support.
Their support stems from massive frustration over the political establishment's implication in two major financial scandals: the country's 2008 banking crash, and now the Panama Papers leaks.
Icelanders generally have little else to complain about. The country boasts full employment, low crime levels, a well-functioning welfare state, low income inequality and a high life expectancy of 83 years.
A poll at the end of March suggested that just three per cent of voters had a favourable opinion of him.