Parents of murdered US journalist Daniel Pearl appeal acquittals
A Karachi court sparked outrage last month when it acquitted British-born militant 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.
"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 prosecutors already filed with the court.
Following the acquittals, authorities re-arrested Sheikh and the others, who will be held for at least three months while the appeals play out.
Pearl's killing provoked international condemnation, pressuring Pakistan's military government just as it was remaking its image following years of backing the Taliban in neighbouring Afghanistan.
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 Pakistani 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.
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 Islamist militants.
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."
Agencies contributed to this report.