PESHAWAR: Eight of the 10 men acquitted by a court over the attempted murder of Malala Yousafzai are still being held in custody on other charges, officials said Saturday.

Court and security officials said last month 10 men had been convicted in a secret trial by an anti-terrorism court and jailed for life over the October 2012 attack in which the teenager was shot in the head on her school bus.

But in a surprise twist on Friday, officials said that in fact eight were cleared and only two sent down for their part in the bid to silence education campaigner Malala, who last year became the youngest ever Nobel Peace Prize winner.

Know more: Eight of 10 accused in Malala attack case acquitted.

The suspects' trial was held behind closed doors at a military internment centre and even its existence was not known until the verdicts were handed down in April.

Police said Saturday that the eight men who were cleared were in fact still in custody.

“The eight who were acquitted are still being held in various jails and an internment centre,” a police official who followed the trial and had access to documents relating to the case told AFP.

The eight had various other terrorism-related charges against them, he said.

“The trial was held at internment centre Swat which is controlled by security forces and access of media, even police, is restricted,” the official said on condition of anonymity.

He said police only came to know of the court's decision some two weeks after the hearings, which were conducted by a civilian judge.

Pakistan Army, which wields enormous influence across the country, has a strong presence in Swat and another investigations officer said civilian law enforcement personnel and investigators could not operate freely where the military was in charge.

Malala, now aged 17, survived the attempt on her life and in October last year won the Nobel Peace Prize for her courageous and determined fight for children to have the right to go to school.

The man suspected of actually firing the gun at Malala, named by officials as Ataullah Khan, is believed to be on the run in Afghanistan, along with Pakistani Taliban chief Mullah Fazlullah, who ordered the attack.

Pakistan's military announced the arrest of the 10 suspects in September 2014 as part of an operation that involved the army, police and intelligence agencies.

The announcement of the convictions in April came as a surprise to many, given there was no indication a trial was under way, and until this week officials have done nothing to contradict the reports of 10 men being jailed.

Despite several high-ranking police and legal sources now saying only two were convicted, a senior security official in Mingora on Friday insisted the court had jailed all 10 for life.

The security official accused the police of lying, suggesting divisions between the military and civilian authorities over the handling of the case.

Following a shocking Taliban massacre at a school in December that left more than 150 people dead, Pakistan rushed through legislation allowing military courts to try terrorism cases.

So far these courts have met behind closed doors, announcing only brief verdicts afterwards, prompting sharp criticism from lawyers and rights groups.

After the attack, Malala was taken to the United Kingdom for treatment and has not returned to Pakistan. She has resumed her studies in the UK and said she aspires to one day become prime minister of Pakistan.