Timor-Leste has instituted proceedings in the UN's top court in relation to Asio raids on the office of a Canberra lawyer representing the tiny country.

Australian Security Intelligence Organisation agents raided Bernard Collaery's office this month and seized documents relating to a dispute with Australia over a $40bn oil and gas treaty.

Timor-Leste on Tuesday began proceedings in the international court of justice in The Hague over the seizure of the documents which it says "belongs to Timor-Leste and/or which Timor-Leste has the right to protect under international law".

A statement issued by the court on Wednesday makes clear that Dili wants the ICJ to declare that the Asio seizure "violated the sovereignty of Timor-Leste and its property and other rights under international law and any relevant domestic law".

The documents relate to Timor-Leste's challenge to the treaty on certain maritime arrangements in the Timor Sea. Dili has accused Canberra of bugging its cabinet office during 2004 negotiations on the treaty.

The attorney general, George Brandis, approved warrants for the 3 December raid on Collaery's office and another raid on the home of a former spy who is a key witness in Timor-Leste's case at the permanent court of arbitration.

Collaery said this month that the documents seized included legal opinion by international law experts Sir Elihu Lauterpacht and Professor Vaughan Lowe along with his own correspondence with Timor-Leste's prime minister, Xanana Gusmao.

Dili is arguing at the ICJ that not only was the seizure of the documents unlawful but so too is their continuing detention.

"Australia must immediately return... the documents and data and destroy beyond recovery every copy of such documents and data that is in Australia's possession or control," it is demanding, according to the ICJ statement.

Timor-Leste wants a "formal apology" and for the court to rule that all of the documents seized be immediately handed over to the ICJ. It also wants a list of which documents have been passed to which people and their job descriptions.

Finally, Dili is demanding that Australia not spy on Timor-Leste: "Australia [must] give an assurance that it will not intercept or cause or request the interception of communications between Timor-Leste and its legal advisers whether within or outside Australia or Timor-Leste."

Collaery has said he's considering legal action against the Asio boss, David Irvine, over his involvement in the alleged 2004 bugging of Dili's cabinet office. Irvine was then director general of Australia's overseas spy agency, the Australian Secret Intelligence Service.

Gusmao condemned the raids as "unconscionable and unacceptable conduct". But his counterpart, Tony Abbott, defended them as necessary to protect Australia's national security.

"We don't interfere in [court] cases but we always act to ensure that our national security is being properly upheld – that's what we're doing," he said at the time.