The US State Department on Friday expressed its reservations after the Sindh High Court (SHC) ordered that the four men charged in journalist Daniel Pearl's abduction and murder case be released immediately, terming their detention illegal.

In a message on Twitter, the state department said it was "deeply concerned" at the Dec 24 ruling of the SHC to release "multiple terrorists responsible for the murder of Daniel Pearl".

"We have been assured that the accused have not been released at this time," the statement added.

It said the department will continue to monitor any developments in the case and will continue to support the Pearl family "through this extremely difficult process" while honouring the legacy of Daniel Pearl as a journalist.

The statement came a day after the SHC struck down a preventive detention order issued by the Sindh government to keep four men behind bars after their convictions by a trial court were set aside around eight months ago in the abduction and murder case of US journalist Daniel Pearl.

The bench also barred the federal and provincial authorities from placing the men under any preventive detention order without prior permission of the SHC. However, their names were placed on the no-fly list and they were also directed to appear before the court whenever summoned.

In April, the high court had acquitted all the appellants of the charges of murder and kidnapping for ransom and only found main accused Ahmed Omar Sheikh guilty of abducting the slain journalist and sentenced him to seven-year imprisonment. However, the sentence had been completed as the convict had already spent around 18 years in detention.

The Supreme Court is hearing the appeals of provincial government and the parents of the slain journalist against the SHC’s order.