In filing the case in Sweden's Court of Appeal of Svea, representatives for Assange said, due to the "unlawful" deprivation of his liberty, officials in Stockholm, "must release and compensate him immediately for the harm caused.
"Despite never having been charged with any offense, while visiting the United Kingdom police seized his Australian passport and imprisoned him on Sweden's request," Assange's legal representatives said in a statement.
"For six years now, his rights have been severely violated, as have the rights of his children. WikiLeaks started its publication of US diplomatic cables on November 29, 2010, a week before Sweden and the UK arbitrarily imprisoned him."
The stalemate surrounding Assange's case took a change of direction in February this year, when a UN working group ruled that the 45-year-old had been "arbitrarily detained" as a result of his four-year long stay in the embassy, as he had not been allowed to leave the building without the threat of arrest.
Question: Has Assange received a renewed Australian passport yet? United Nations deemed him Arbitrarily Detained back in Feb 2016 @wikileaks— Jude Fleming (@flemingjude) June 6, 2016
British officials rejected the working group's non-binding opinion, calling the report "deeply flawed." Meanwhile, Assange's latest appeal has put pressure on Sweden to adhere to the UN findings.
"The proceedings will test whether Sweden complies with its binding treaty obligations and whether it acts in good faith under the UN human rights system," a representative of Mr Assange's legal team said.
History of Disagreements
Assange, who was first taken into custody at London's Wandsworth prison in 2010, was then living under house arrest and has been living in Ecuador's UK embassy for more than four years.
After exhausting all legal options in the UK aimed at avoiding extradition to Sweden, he was granted political asylum in Ecuador in 2012.
The Australian has never formally been charged with any offense in Sweden, with investigators stating that they want to interview the WikiLeaks founder before making a decision on sexual assaults claims.
Despite offers from Assange to be interviewed in London's Ecuadorian embassy, no agreement between Swedish and Ecuadorian officials has yet been struck.
Citing an outstanding European arrest warrant, British officials have stated that they will arrest and extradite the WikiLeaks founder to Sweden should he leave the embassy in London.
However, Assange has rejected calls to travel to Sweden to speak to authorities, amid fears he could be then extradited to the US over his role in the leaking of thousands of sensitive government documents.