Iceland's Pirate Party, founded by anarchists, activists and former hackers, recorded a historic breakthrough in Saturday's snap election, as the government, rattled by the Panama Papers scandal, lost ground, according a TV poll.

It is, however, uncertain if the "Pirates" will be able to form a majority with its centre-left alliance, as partial results of six legislative districts show a tight race with the incumbent centre-right government.

After early counting the Pirates appeared to be running third.

The negotiations could last for days or weeks if the Pirates-led alliance or the government do not gain the necessary 32 of the 63 seats in the Icelandic parliament, the Althingi.

In the latest wave in a global movement against mainstream politics, the "Pirates" won 12 seats, quadrupling their showing since 2013, according to the RUV state television predictions.

"We are very satisfied," said Pirate cofounder Birgitta Jonsdottir, an activist, poet and WikiLeaks supporter.

"Whatever happens we have created a wave of change in the Icelandic society. The results are awesome," she told a cheering crowd in Reykjavik.

The preliminary figures came after the polls closed at 10:00 pm (2200 GMT) and were greeted with applause by activists and "pirates" inside a bar in Reykjavik, crowded with tourists and foreign press.