Ukraine's chief prosecutor says "criminal negligence" by pilots and military officials caused the world's worst air show disaster.

Prosecutor-General Svyatoslav Piskun said the pilots had used an illegal flight path when their Soviet-era Su-27 fighter jet ploughed into the crowd at the Sknyliv air base near Lviv in western Ukraine on Saturday, killing at least 83 spectators.

The plane ploughed into crowds of spectators

He said senior officials, including Ukraine's air force commander Viktor Strelnikov, had already been detained in connection with the crash.

The news came as more than 1,500 Ukrainians gathered at the scene of the accident to attend a memorial service for the victims.

On Monday, the Defence Ministry suspended the flights of virtually all military aircraft.

Human error

At a news conference in the capital, Kiev, Mr Piskun spoke of "circumstances testifying to criminal negligence and careless treatment of responsibilities by officials".

"I believe that it is already possible to say that this was military negligence, a special category of crime," he said.

Click here to see how the tragedy unfolded

"There were many incidents when criminal negligence came into play, when several heads of Ukraine's air force acted criminally...

"We believe that the pilots were given the wrong task with violations of safety procedure."

But he went on to blame the pilots, noting "signs of criminal offence".

"They used this vehicle incorrectly," he said, adding they could either be detained or put under house arrest pending the outcome of the investigation.

On Sunday, President Leonid Kuchma fired the armed forces chief of staff, Petro Shuliak, a day after sacking General Strelnikov.

Defence Minister Volodymyr Shkidchenko submitted his resignation on Sunday.

Grief

The Su-27 was performing aerobatics when it clipped the tops of trees before cartwheeling across the air base and ploughing into crowds of spectators.

Twenty-three children were among those who died. Nearly 200 people were injured in the crash and officials have warned the death toll might climb.

Forensic experts are still trying to identify victims at a city morgue, but the process is slow because many of the bodies were mutilated beyond recognition.

Hundreds of relatives of the dead and spectators who survived the disaster, clutching carnations and handkerchiefs, streamed into the base on Monday, attending a two-hour memorial ceremony led by Ukrainian Orthodox clerics.

Flowers were strewn around the singed turf where the fighter jet exploded.

One of the priests conducting the service, Father Zynoviy, called for people to rally around each other.

''Our region has never experienced such grief,'' he said.

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