The event was staged to recognise the efforts of the Armed Forces
Five people have been arrested and another eight taken into custody during an Armed Forces Day event in Glasgow.
One person was injured in George Street where sectarian songs and chants were sung, as a service was conducted in nearby George Square.
Events are being held in towns and cities across the UK to allow the public to show its appreciation for the work of serving personnel and veterans.
The trouble has been condemned by Scottish Secretary Jim Murphy.
The protestors were believed to have been from an Irish Republican group. Supporters of the event were also involved in noisy confrontations.
Strathclyde Police said 12 men and a woman, between the ages of 20 and 30, were taken into police custody, five of whom were arrested.
The remaining eight have been detained and are being interviewed by police.
A 24-year-old man, who received a head injury as a result of the disturbance, was taken by ambulance to Glasgow Royal Infirmary.
Mr Murphy, who himself was targeted by a group shouting religious abuse, described the disruption as "sickening".
He added: "I was proud to be part of Armed Forces Day in Glasgow today and so proud of these brilliant men and women in uniform. They are Britain at its best and Scotland at its bravest.
"At the other end of the spectrum, the event was soured by a tiny minority of mindless demonstrators who can't begin to understand the meaning of bravery and what the veterans have done for our country.
"A separate group of mindless idiots also soured the day for me. After doing an interview for BBC, I was subjected to sustained sectarian abuse from people who seemed to take great and foul-mouthed offence because I am Catholic."
Speaking after the event, Assistant Chief Constable George Hamilton, of Strathclyde Police, said: "It is extremely disappointing that a number of people marred what was a celebratory parade with this despicable and completely unacceptable behaviour.
"Please be assured that a thorough investigation will follow today's event and anyone responsible for causing the disruption who was not detained by officers at the scene today will be tracked down and dealt with appropriately."
Members of the armed forces took part in the Glasgow parade
Those arrested are expected to appear at Glasgow Sheriff Court on Monday.
The event marks the first time an Armed Forces Day has been held.
Parades, flypasts and parachute displays are honouring the role of the military in towns and cities.
The George Square parade was being led by veterans and veterans' associations followed by serving military who marched with the band of the Royal Regiment of Scotland.
An Army spokesman earlier said it was thrilled the people of Scotland had embraced the concept of the day.
Brigadier David Allfrey, co-ordinator of Armed Forces Day in Scotland, said: "Communities have been honouring the armed forces over the last couple of weeks.
"This is a homecoming and a great day for all the family."
Support and gratitude
In Scotland's capital, a parachute display by the Army's Golden Lions which was due to take place above Holyrood Park and a fly-past by an RAF Nimrod had to be cancelled due to poor weather conditions.
However, a march of 500 military personnel, including the Royal Scots Dragoon Guards, went ahead.
City Lord Provost George Grubb earlier said: "Here in Edinburgh, we will be honouring our armed forces past, present and future with a fantastic day for all the family to take part in, watch and enjoy.
"Our armed forces, both serving personnel and veterans, need our continued support and gratitude for the risks they take to keep us safe.
"Sending people to war is a huge responsibility and remembering them when they return is just as important."
In Aberdeen an RAF Nimrod flew over Union Street.
In Dundee, veterans were joining serving members of the Army, Navy and RAF in Dundee for a procession and march to City Square.
On Sunday, a parade and veterans badge presentation is being held in Forfar.