The parents of murdered US journalist Daniel Pearl filed an appeal with the Supreme Court of Pakistan on Saturday to reverse a decision overturning the longstanding convictions of four men in the case.

The Sindh High Court (SHC) had last month acquitted the main accused, British-born Ahmed Omar Saeed Sheikh, and three other men convicted in Pearl's 2002 kidnapping and beheading.

“We have filed an appeal of this decision to the Pakistan Supreme Court,” Pearl's father, Judea Pearl, said in a video message.

Examine: Will Pearl’s killers ever be brought to justice?

“We are standing up for justice not only for our son but for all our dear friends in Pakistan so they can live in a society free of violence and terror and raise their children in peace and harmony.”

The appeal doubles up on a petition filed last month by the Sindh government challenging the SHC decision in the apex court.

Earlier this week, the Sindh government requested the Supreme Court to fix the hearing of its appeal as early as possible, preferably in the coming week, citing an apprehension that Sheikh could abscond.

Following the acquittals, authorities in Sindh re-arrested Sheikh and the others, who will be held for at least three months while the appeals play out.

Faisal Siddiqui, the lawyer representing Pearl's parents, told AFP there is “substantial incriminating evidence, both oral and forensic, against the accused persons for the offences they have been tried for”.

The “Sindh High Court has misapplied the burden and the standard of proof erroneously to the facts of this case”, their appeal states.

Tariq Bilal, a senior lawyer, said the court would take up both appeals simultaneously.

The “filing of the appeal by parents alongside the state would carry greater weight for the court as both parties have questioned the acquittal”, Bilal said.

The chief US diplomat for South Asian affairs, Alice Wells, in a tweet appreciated the appeal filed by the government against the acquittals.

"We appreciate the Govt of Pakistan's 4/22 appeal to reinstate guilty verdicts against Daniel's murderers, now buttressed by the filing of the Pearl family's appeal before the Supreme Court," read the tweet, coming on the eve of World Press Freedom Day.

Pearl was South Asia bureau chief for The Wall Street Journal when he was abducted in Karachi in January 2002 while researching a story about religious extremism.

A graphic video showing his decapitation was delivered to the US consulate nearly a month later.

Observers at the time said the killers were acting out of revenge for Pakistan's support of the US-led war on the hardline Taliban regime in Afghanistan and the Al Qaeda terror network they harboured.

In a statement supporting the appeal, the Committee to Protect Journalists said releasing the four men in the case "would only add to the threats facing journalists in Pakistan and deepen Pakistan's reputation as a haven for terrorists".