Pakistan's Supreme Court has ordered the release from prison of Ahmad Omar Saeed Sheikh, a ringleader in the kidnapping and murder of US journalist Daniel Pearl by al-Qaeda and Pakistani Islamist militants in 2002.

Pakistan's government had appealed to the court on Friday to review its decision to free the British-born Islamist and three others convicted in the case, a day after their acquittal by a panel of three judges.

The United States also expressed concern over Sheikh's acquittal, and US diplomat Antony Blinken repeated a call for accountability in his first phone call with Pakistan's foreign minister on Friday.

The review panel, headed by Justice Omar Ata Bandyal, stood by the decision to acquit, and recommended that Sheikh should be moved to a "rest house" before being fully released.

"He should be moved to a comfortable residential environment something like a rest house where he can live a normal life," the judge said.

Daniel Pearl was murdered in 2002

As the government makes the arrangements in next two days, Sheikh will be kept in a comfortable environment in the jail with a permission to see his family, the court said.

"It is not a complete freedom. It is a step toward freedom,"his father said.

The terms of Sheikh's release will become clearer once a written order is made public.

Ahmed Omar Saeed Sheikh pictured after his arrest in 2002

On assignment for the Wall Street Journal in the months after the 11 September 2001 attacks on the US, Mr Pearl was kidnapped in Karachi and later murdered.

Al-Qaeda's number three leader Khalid Sheikh Mohammed confessed to killing him, and Sheikh, a former student at the London School of Economics, had played key role in luring the journalist into a trap.