We are investigating all the matter to find out how the incident took place, who was involved in the assassination and who was behind it

Abdul Khaliq Fazal, Public Works Minister

Two cabinet members - the Labour and Social Affairs Minister, Mir Wais Sadeq, and the Public Works Minister, Abdul Khaliq Fazal - are heading the inquiry team.

They were named by interim leader Hamid Karzai on Monday.

Analysts say the appointment of such senior officials to investigate the murder reflects the sensitivity of the case which has laid bare deep divisions within the interim government.

Mr Rahman was beaten to death at Kabul airport last Thursday.

Conspiracy?

The attack was initially blamed on pilgrims on their way to Mecca who were angered by long delays to their flights.

Abdul Rahman: Victim of personal feud?

But Mr Karzai later blamed the murder on Mr Rahman's long-running personal feud with some officials in the intelligence, defence and justice ministries.

Seven people have been arrested in connection with the killing.

Mr Karzai had demanded the extradition of two other suspects from Saudi Arabia.

But the public works minister said he was informed on Wednesday that there were no suspects in Saudi custody.

"One day we are told two people are arrested, another day we are told the opposite" he told the Associated Press news agency.

"We will investigate this matter", Mr Fazal said.

He said the Afghan attorney general's office would question those detained.

Internal rift

Several of those wanted in the case are senior members of Jamiat-e-Islami, the dominant faction in the Northern Alliance.

The killing has raised security fears

Mr Rahman abandoned Jamiat-e-Islami some years ago after an internal dispute.

The Afghan police are also investigating his murder.

But analysts say the police is dominated by members of Jamiat-e-Islami.

They say Mr Karzai's choice of investigators apparently reflects concern that the police might be influenced by their ethnic and political affiliations.

There has been speculation that the killing of Mr Rahman may be linked to a rift between Jamiat-e-Islami loyalists within the interim administration and those loyal to the exiled king, Mohammad Zaher Shah.