Media playback is unsupported on your device Media caption Men were filmed setting birds on each other

Animal welfare charity the USPCA has said it was "shocked and stunned" by the number of people taking part in organised cock fighting.

The illegal fights take place regularly at venues on both sides of the Irish border.

BBC Newsline has had exclusive access to an Ulster Society for Prevention of Cruelty to Animals investigation.

The USPCA's Stephen Philpott said the organisation had been investigating the fights for two years.

"Over the years, the USPCA would get wind from time to time of individual cock fights, a lot of those were associated with the Travelling community, and they were one-offs," he said.

"When we entered this investigation, we thought that's what we'd be looking at, unfortunately it wasn't- this is a very highly organised business.

"It was the number of spectators at the events that stunned us - people from all walks of life coming out to watch chickens tear each other to bits."

For months now BBC Newsline has had exclusive access to the USPCA investigation.

At one site last weekend, about 60 people, some of them children, were gathered around a makeshift ring in County Monaghan about five miles from the border with Middletown in County Armagh.

On another occasion, both birds seemed to survive. In an earlier encounter one of the birds was lifted, apparently lifeless, from the ring.

These big events in the cock fighting world are known as derbies.

Agitated to fight

On St Patrick's Day this year, another meeting took place just south of the border.

Cars, vans and hatchbacks transported the birds in cages where they are penned before being agitated to fight.

Again birds died in the ring. Children were there - a young boy was pictured taking care of one of the birds that survived.

Mr Philpott said the USPCA had hundreds of hours of footage, but do not know who to give it to, whether councils, the Department of Rural Development or the police.

He said those taking part had an arrogance that they would not be caught.

"There are two shots that do it for me," he said.

"One is the sight of a postman arriving in the middle of a derby chicken fight, which is a huge international chicken fight.

"The postman arrived to deliver his letters, was completely not put off by the number of people or what they were doing, delivered his letters and left.

"The other one was the sight of a burger van there to feed the people as chickens were being fought."