A Libyan government spokesman says Australian lawyer Melinda Taylor can buy her freedom by leading authorities to a key former regime figure linked to Moamar Gaddafi's son Saif al-Islam.

Ms Taylor is being held in what the Libyan government says is "preventative detention" after being arrested in the town of Zintan last week.

The local Zintan Brigade militia which is holding Saif claims Ms Taylor tried to give Saif a coded letter from his former henchman Mohammed Ismail.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 35 seconds 3 m 35 s Mohamad Al-Hereizi speaks to AM Download 1.6 MB

Ms Taylor was in the town with an International Criminal Court team to meet Saif ahead of his upcoming war crimes trial.

Now Libyan government spokesman Mohamad Al-Hereizi says he and the rebels believe that Ms Taylor knows where Mohammed Ismail is hiding.

Asked by the ABC's AM program if "after she tells you where Mohammed Ismail is, then you will let her go?", Mr al-Hereizi replied: "Yes".

Who is Mohammed Ismail? Formerly the right-hand man of Moamar Gaddafi's son, Saif al-Islam

Formerly the right-hand man of Moamar Gaddafi's son, Saif al-Islam According to cables released by Wikileaks, he was born July 6, 1968 in Alexandria, Egypt

According to cables released by Wikileaks, he was born July 6, 1968 in Alexandria, Egypt Spent his childhood travelling abroad with his diplomat father

Spent his childhood travelling abroad with his diplomat father Lived in Afghanistan in the late 1970s as a child and attended the American School in Kabul

Lived in Afghanistan in the late 1970s as a child and attended the American School in Kabul Described in the cables as "soft-spoken" and spoke fluent English

Described in the cables as "soft-spoken" and spoke fluent English Features in US cables that detail discussions about a weapons-grade uranium shipment, bound for Russia and held up on a runway in Libya

Features in US cables that detail discussions about a weapons-grade uranium shipment, bound for Russia and held up on a runway in Libya Described by the Guardian as "Saif's fixer – intelligent, discreet and powerful"

Described by the Guardian as "Saif's fixer – intelligent, discreet and powerful" Worked for the Gaddafi regime from a huge suite in a guarded compound in Tripoli

Worked for the Gaddafi regime from a huge suite in a guarded compound in Tripoli After civil war broke out in April 2011, he took a trip to London, saying he was visiting family, and held talks with British officials

After civil war broke out in April 2011, he took a trip to London, saying he was visiting family, and held talks with British officials During these talks he reportedly proposed a scenario under which Gaddafi's sons would retain some power while their father stepped aside with his honour intact

Mr al-Hereizi says authorities who searched Ms Taylor found GPS coordinates which they believe are linked to Ismail.

"She has paper from him. That means she see him. I don't know where. She saw him. Yes. We want this guy. It's very important to catch this guy because this guy is very, very, very dangerous for us."

Asked by AM: "Do you think she understands how important he is to Libya?" he replied: "She know. She know."

"We don't have anything against this woman. Just we need some information from her, after that she will be free."

'Preventative detention'

As a defence lawyer appointed by the ICC Ms Taylor is supposed to have diplomatic immunity.

Overnight the ICC demanded her immediate release, along with that of the other three members of the ICC team.

Libyan officials say Ms Taylor and the three other ICC staffers have been put in what they describe as "preventive detention" for 45 days while they are investigated.

Foreign Minister Bob Carr, who has sent a senior diplomat to Libya to look into the case, says it is essential that Australian embassy staff be granted immediate access to her.

Her boss at the ICC, Xavier-Jean Keita, has told the ABC that Ms Taylor is an ethical person and says her arrest is illegal.

"They are ICC staff with privilege and immunity," he said.

ICC spokesman Fadi el-Abdallah said he was trying to find out why members of the team will be held for up to 45 days.

"We don't have direct contacts with the members of the delegations," he said.

"The Libyan authorities did not provide us with any official information saying that there are any charges against any member of the delegation.

"They didn't provide us with any official information about the circumstances or the conditions of the detention."

Carr concerned

Meeting: Saif al-Islam Gaddafi on a plane in Zintan after his capture on November 19, 2011. ( Reuters: Ismail Zitouny )

Australia's ambassador-designate David Ritchie is in Libya and is seeking urgent access to Ms Taylor.

Senator Carr says he is concerned by reports she has been moved from house arrest.

In a statement, he said it was essential for Libyan authorities to grant immediate consular access to Ms Taylor and her colleagues.

"There is a need for caution in all public statements on a matter such as this," he said.

"However, the Australian Government is very concerned that Ms Taylor has reportedly been moved, and has so far not been permitted contact with either a representative of the Australian Government, the ICC or her family."

Senator Carr said he had spoken to Libya's deputy foreign minister Muhamed Aziz on two occasions in the last 24 hours, as well as Britain's ambassador to Libya, the president of the ICC, and members of Ms Taylor's family.

But Libyan government spokesman Mohamad Al-Hereizi has told AM that media reports suggesting Ms Taylor has been transferred to a prison are incorrect.

"No. There is no jail in Zintan, believe me. The jail in Zintan is broken," he said.

"She [has been] taken to a very, very, very good situation."

Mr Hereizi said Ms Taylor was being kept in a house where she would stay for days, possibly weeks.

He said the Zintan Brigade militia which is holding Saif believed Ms Taylor knew the location of Mohammed Ismail.