The safety of prison staff has been given the "highest priority" following two disturbances at a maximum security jail, Scotland's justice minister has promised.

Jim Wallace said he had held a "constructive" meeting with the head of the Scottish Prison Service (SPS) to discuss the unrest at Shotts Prison, which caused damage estimated at £1m.

However, he said there was no obvious link between the two incidents at the Lanarkshire jail in the space of a week.

Mr Wallace called for the meeting with SPS chief executive Tony Cameron following the second incident, which left three prison officers injured.

The first riot took place at New Year

Later, Mr Cameron and Audrey Park, governor of HMP Shotts prison, made their first visit since the unrest to the Shotts Unit, a self-contained prison within the jail.

The prison's A Hall, which sustained the worst damage, is not expected to be ready to re-house prisoners for at least two months.

The 115 inmates previously housed in A Hall have now been transferred to five other jails.

The justice minister said lessons had to be learned - but violence in prison was to be expected.

"When staff have been injured I wanted to know if there was anything that could have been done - it's not clear that there was.

Knife-proof vests

"But it was important that we did actually try to see, and continue to try to see, if there is any pattern emerging.

"If you can do that then obviously you can take measures which can reduce the risks of this happening again," he said.

Mr Wallace said that the refurbishment of Shotts' A-Hall would include improved security arrangements.

He also suggested that officers should be issued with knife-proof vests similar to those worn by police.

However, the Prison Officers' Association has called for an investigation into better equipment to protect staff.

Ultimately you can't have a 100% free of risk environment Tony Cameron SPS chief executive

It said that the currently available vests would prevent staff working with prisoners to address offending behaviour.

Mr Wallace added that more work needed to be done to identify some of the key ingredients in the two separate incidents at Shotts.

He said a tough policy against drugs appeared to have "triggered" the first disturbance.

However, there was "no obvious evidence" of a link between the two incidents.

Mr Cameron said he wanted to avoid a "knee-jerk reaction" to the disturbances.

"Ultimately you can't have a 100% free of risk environment, it's a balance," he said.

Broken leg

"Over the next few days and weeks we will have a look at whether we can alter the regime, and our deployment at Shotts, to see whether there are improvements that can be made."

Three officers were stabbed during trouble at the jail on Tuesday night.

Three men have appeared in court in connection with the incident.

One officer broke his leg during a 19-hour siege, involving 80 prisoners, at the prison a week earlier.