Firefighters in Ireland were forced into using an angle grinder to remove a metal ring that had become stuck on a man's penis and causing a rare case of "penile strangulation".

The unnamed man was caught with his pants down in Dublin with doctors at Mater University Hospital saying that he was suffering genital pain and swelling.

Standard equipment used by doctors to remove the ring was rendered useless because it was made of titanium, one of the hardest metals on earth.

The Irish Medical Journal (IMJ) said the man had put on the ring seven hours earlier but had to go to hospital when the pain became unbearable.

Penile strangulation requires urgent treatment by medical experts as a loss of blood flow to the penis can lead in severe cases to amputation.

The IMJ paper said that the man was sedated with a mixture of ketamine, fentanyl and propofol.

He remained sedated for the 20-minute procedure as fire officers cut the ring in two with a hand-held angle grinder. Fire protection sheets were laid around the operation area to prevent damage from sparks.

The BBC reported that the man made a "full functional recovery".

Rings can be used to increase sexual pleasure and performance and come in a range of materials including metal, plastic and silicone.

It is recommended that users purchase silicone constriction rings as they are more malleable. It is also advised that the products should be used for a maximum of 30 minutes.

Cases of penile strangulation are extremely rare worldwide. According to a 2013 study just 120 cases have been reported in medical journals worldwide in the last 200 years.

In one notable case a 72-year-old man suffered unnatural swelling for more than a month.