A young boy was beaten "black and blue", as though he had been in a boxing match, after catching two nuns in an embrace, an inquiry has heard.
A man said he was six or seven when one of the nuns went "mental" and "ballistic" as she lashed out at him in a boiler-room at a care institution in the 1960s.
He told Scotland's child abuse inquiry that the "vicious" assault left him with bruises for weeks and with blood coming out of his ear and nose.
He described the reaction as "exceptionally over the top" and said it left him feeling constantly threatened.
The witness, who cannot be identified, made the statements as he told the inquiry of his experiences at Smyllum Park orphanage in Lanark, South Lanarkshire, which closed in the 1980s.
He said he moved to the orphanage, run by the Daughters of Charity of St Vincent de Paul, in the mid-1960s, where he was never given any love, affection or praise from the nuns and staff members who ran it.
Physical abuse in the form of slaps and kicks was routine "for trivial stuff", he told the hearing in Edinburgh.
The man recounted one incident in which he walked past a boiler-room and went through an open door to have a look inside.
He said: "There were two nuns in there and one nun had her arms around the other one, at which point she turned around and gave me a right good hiding.
"I'm talking about punching, kicking, pulling my hair.
"I distinctly remember there was a boiler and it had a flame coming out of it, a flame thrower ... She put my face really close to that.
"I can still remember my hair getting singed, my eyelashes and the smell of singeing stayed with us for quite a while after that."
When he "woke up" from the attack, he had "blood coming from my ear, blood coming from my nose", the inquiry heard.
"For days after that, I was black and blue, like being in a boxing match actually."
He said he wondered for a long time what had caused the nun to be so "nasty" until he found out about one of television's first lesbian kisses on the soap Brookside.
"She was obviously kissing another nun, that's what I think," he said.
Asked about the impact of the assault, he said: "It was terrible, it was horrendous, really bad. I felt threatened all the time, constantly on my toes, just always, always on guard."
He went on to describe another incident in which a staff member slapped him on the face and knocked him unconscious after catching him in an orchard.
He told how he was later moved to another institution in England.
During his time there, he experienced sexual abuse at the hands of a trainee priest, the inquiry heard.
He told how the enforced move really affected him, having "robbed" him of his Scottish identity.
The witness said in an earlier statement that he hoped the inquiry would be "strong enough to take on the Catholic people".
He told the inquiry: "I'm telling you now, you will not beat them ... good luck."
Another witness told the inquiry he has a fear of nuns after suffering physical, emotional and mental "torture" at Smyllum.
The man - whose name cannot be disclosed - spoke of regular "thunderous" beatings at the hands of the nuns tasked with looking after him.
The witness told how he was taken to Smyllum for a time at the age of four following the death of his mother.
He said the nuns would beat him, kick him and strike him with implements such as wooden coat hangers.
"The punishments were frequent and the beatings were thunderous," he said.
He also spoke of verbal abuse from the "callous" sisters, telling the hearing: "The nuns would say things like 'your ma's left you for good'."
He said: "Being there at Smyllum, it was physical, emotional and mental torture."
The witness told the inquiry he has "an absolute fear of nuns".
He added: "The people behind the beatings were always nuns. The people who were supposed to be looking after (me), they were absolutely unforgiving."
The inquiry, chaired by Lady Smith, continues.
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