A couple in their 50s had to be rescued after they became trapped in an "impenetrable jungle" of rhododendron plants on an Irish mountainside.

The hillwalkers endured a five-hour ordeal in the Knockmealdown Mountains last Sunday before their nightmare was ended by a successful and dramatic rescue operation.

Rescuers have described the operation as one of the most hazardous they have been involved in, with one volunteer likening the terrain on the mountain range - which straddles the border between County Waterford and County Tipperary - to "an impenetrable jungle".

The couple, who are experienced hillwalkers, got into difficulty on a steep hillside that sloped down to a lake.

Although rescue volunteers located them quickly and managed to get into a position just 400 meters away, they did not anticipate just how difficult it would be to reach the couple through the thick vegetation.

Jimmy Barry, from the South Eastern Mountain Rescue Association, said the operation - which also involved a river rescue team and local gardai - was one of the most challenging ones he had ever been involved with.

He said it was made even more difficult by the fact that the foliage was so dense, it meant people could not hear each other.

Speaking to BBC Radio Ulster, he said: "It was horrendous - I have been a member of mountain rescue for 15 years and it was probably one of the most dangerous exercises or rescues I've been on.

"We sent the first party of five in - I was in that party - and within 50 meters, we couldn't move, but did not anticipate how difficult it would be to reach the couple through the dense vegetation.

"And it was messy, we had to crawl through it, carry our gear and then try and locate the people as well."

Barry also told the BBC that he had never witnessed his rescue team struggle so much among rhododendrons, recalling how it two hours to walks just 350 meters.

"We kept going. Two hours later we finally reached the two people inside the middle of the rhododendron forest, and then the 'fun' began, because we had to decide how we were going to get out of it.

"We were 100 meters from the edge of the lake, so we decided to literally drop down the forest."

Barry also told the program that because the plant's dense foliage tends to block out sunlight and kill off surrounding vegetation, it produced very tricky terrain on the moutainside.

He continued: "It's regarded as weed. It's not a native plant to Ireland or any part of the British Isles and they've just gone wild. It looks wild, but underneath it nothing of our native plants grows, and it's just horrible in there.

"Dangerous, because where it was growing on the side of the lake, it's very steep ground, so were literally walking on rhododendron.

"We could look through the rhododendron and see 10ft drops, 20ft drops and at the end were looking at a 50ft drop, but we had to go down through it to get out."

The couple, from Munster, and their rescuers eventually reached the lake where they were picked up by a boat and taken to safety. Despite their ordeal, they suffered no injuries.