A teenager caused £30,000 of damage during a seven-hour rooftop siege with police.

The boy, then aged 15, was being held at Rossie Secure Unit in Montrose, Angus, when he and another boy sparked a standoff that led to almost 30 police officers being called to the scene.

During the incident they stripped an area of roof clean of tiles and used them to cause thousands of pounds worth of damage to police cars and staff vehicles.

Dundee Sheriff Court heard the day before the attack the boy had been told he would be leaving the unit on his 16th birthday due to his "aggressive and violent" behaviour.

He then told his family he was "upping the ante" in a bid to get a jail sentence.

Police were later called after he made threats to staff, resulting in him punching an officer who attended.

The following day another teenager, who was previously prosecuted over the incident, robbed a staff member at the unit of her access pass for the building and used it to release the accused from his locked room at 4.30pm on February 8.

Fiscal depute Vicki Bell told the court: "Both boys then embarked on a spree of vandalism, destroying property within the buildings including six doors, one window and two photocopiers.

"Both then armed themselves with scaffolding poles which they used to force open doors and make their way through the building, presumed to be in an attempt to break free.

"Both then climbed on to a roof within the courtyard before climbing on to the roof of an adjacent building."

Both boys threw slates and other debris at vehicles in the car park.

It resulted in two police vehicles as well as other cars belonging to staff being damaged.

She added: "Police attended and a cordon of eight officers surrounded the buildings. Fire and ambulance attended to provide assistance via a high aerial platform used to allow a visual perspective of where the accused were.

"Further police resources were required, including a dog unit, eight members of the operational support unit, police support unit officers and a police support unit tactical adviser."

She continued: "A negotiation coordinator and two negotiators were brought to commence dialogue with the boys.

"Both continued to throw slates off the roof towards police, but no one was struck.

"Substantial damage was caused to the roof as large areas were stripped of tiles subsequently smashed on the ground below.

"A further nine officers arrived to assist in securing the building.

"Following a lengthy stand-off at about 11.30pm, both boys agreed to come in off the roof and were arrested."

Tiles were completely stripped from the roof where both boys had been on. The damage to the building cost about £14,000 while the staff vehicles cost more than £13,500 to repair.

Fiscal Bell said: "Police vehicles sustained £3,300 of damage.

"The trust that operates Rossie had to pay a £5000 excess on the damage to the building and a further £5,000 excess for damage to their cars."

The 16-year-old, of Lanarkshire, pleaded guilty on indictment to charges of assaulting police constable Mark Garnes on February 7 and culpable and reckless conduct committed on February 8.

Both incidents occurred at Rossie Young People's Trust.

Sheriff Alastair Carmichael deferred sentence until January next year and continued the teenager's bail meantime.

The court heard that since the incident the boy has been jailed for a total of 22 months over a string of incidents and faces sentencing in January at Lanark Sheriff Court over a gun robbery.