Megaupload boss Kim Dotcom has launched an online song attacking US President Barack Obama and urging supporters not to vote for the US leader, who he accuses of trampling on Internet freedom.

In a song titled "Mr President" released on YouTube, the self-styled cyber freedom fighter, who allegedly masterminded a massive online piracy business, compares himself to US civil rights campaigner Martin Luther King.

Dotcom, free on bail in New Zealand awaiting a US attempt to extradite him for alleged copyright theft, raps "don't vote for those who would take us back in time".

"What about free speech Mr President, what happened to change Mr President," the German national continues in the song, which has attracted almost 500,000 views since it was posted on YouTube on Sunday.

He also complains "Hollywood controls politics" and "the government is killing innovation".

The clip uses footage of civil rights protests from the 1960s as Dotcom sings "I have a dream like Dr King", and more recent pictures of Occupy movement demonstrators wearing Guy Fawkes masks.

A website launched to accompany the song, www.kim.com, features a countdown to the US election in November and asks "if Megaupload.com is not back online by November 1st will you vote for Obama?".

Megaupload and related file-sharing sites were closed in January, when armed New Zealand police cooperating with a US investigation raided Dotcom's luxurious mansion in Auckland.

In a case that US prosecutors describe as the world's largest copyright action, Megaupload, Dotcom and three co-accused have been charged with money laundering, racketeering, fraud and online copyright theft.

The FBI and US Justice Department allege Megaupload sites netted more than $175 million in criminal proceeds and cost copyright owners more than $500 million by offering pirated copies of movies, TV shows and other content.

Dotcom, who denies any wrongdoing, faces up to 20 years jail if convicted in a US court. He is due to appear at an extradition hearing in the New Zealand High Court in March next year.