Trouble flared after the game at the Liberty Stadium as Cardiff fans prepared to leave
Hundreds of Swansea City football fans clashed with police following Tuesday night's Carling Cup match with Cardiff City at the Liberty Stadium in Swansea.
Stones and other missiles were hurled at police lines as Cardiff fans waited to leave the stadium in buses.
Riot police were deployed outside the stadium. Eight fans were arrested and police are calling for a ban on anyone identified in their investigation.
Lord Kinnock, a Cardiff supporter, said he was "outraged" by the clashes.
Speaking on BBC Radio Wales, the former Labour leader said: "I thought our people had learnt their lesson and it is disgusting, it's appalling and it reflects shame on the clubs.
"I just thought we had got through that as far as the Swans and the Bluebirds were concerned and they have just got to learn that it is not acceptable."
The game, which Swansea won one nil, passed off without trouble.
But as the crowds left the stadium, there were reports that some Cardiff fans who were confined in a fenced-off enclosure hurled missiles at the police.
Then the trouble spread across the road where the police were holding back hundreds of Swansea fans to keep the road clear for the Cardiff coaches to come out.
Hundreds of police officers in riot gear kept the home fans clear of the road but missiles including bricks and glass bottles were thrown at Cardiff buses.
Riot police confronted both sets of fans but the worst violence broke out across the road among Swansea fans where the strong police cordon was backed up by dogs and police horses.
Hundreds of chanting Swans fans hurled lumps of concrete, bottles and cans at police.
A fan is led away by police after trouble flared at the football derby
Five arrests were at the stadium and three were in the city centre.
Police have promised a full investigation into what happened involving both clubs.
They are calling for a ban on any fans involved in the violence.
South Wales Police Assistant Chief Constable Robert Evans said: "Whilst the vast majority of spectators were well behaved, a minority made up of several hundred, caused officers and stewards concern throughout the event.
"After the game ended, officers were forced to position themselves in such a way to prevent protagonists clashing. During this, officers were subjected to missile throwing and sustained threats of violence.
"It is of credit to the vast majority of mature fans that they supported police and the clubs and confined their rivalries to the pitch.
"However, the behaviour of others was totally unacceptable.
"It was thanks to the professionalism of the police officers and the stewards that the violence was contained to a small area and did not spoil the enjoyment of the majority of people."
However, ACC Evans said compared to fixtures in previous years, the trouble was limited and confined to a small area.
Swansea City Supporters' Trust chairman Phil Sumbler, who did not see the trouble outside the ground, said eight arrests from a crowd of more than 17,000 suggested the problems were not on a large scale.
"If you were to check that against the figures for some big Premier League games, it's no higher or lower," he said.
"Talking about inside the ground, there were no real incidents of note during the course of the game and the atmosphere was a credit to both sides.
"The fact that there have only been eight arrests might suggest it couldn't have been on a big scale."
The game had been the first major match between the teams in nine years.
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