An elite RUC team trained a Sri Lankan police unit that murdered 10 members of the same family, a widow of one of the victims has claimed in a complaint to Northern Ireland's Police Ombudsman.
The Ombudsman's office confirmed it was considering the Tamil woman's statement that the Special Task Force, a senior member of which visited Belfast in the 1980s to learn RUC counter-terror techniques, slaughtered her relatives.
Darragh Mackin, lawyer for the complainant, said: "The Special Task Force would not have acquired the paramilitary characteristics of the Special Support Unit without the engagement between the RUC and the Sri Lankan Police."
The senior Sri Lankan police officers visited Belfast in 1983 to "see at first-hand the roles of the police and Army in counter-terrorist operations", according to British Government files.
The visit happened months after the Special Support Unit, an elite RUC team, shot dead six men in Co Armagh in some of the most controversial episodes of the Troubles.
Sri Lankan police set up an almost identical unit shortly afterwards, namely the Special Task Force.
Both the RUC and Sri Lankan units consisted of heavily armed officers who underwent special forces training.
The Tamil widow says her relatives were massacred by Sri Lanka's police in 1986 at the height of that country's civil war.
Vairamuttu Varadakumar, director of the Tamil Information Centre, welcomed the case.
He said: "We support the complainant's efforts to seek accountability for the brutal violence against their family."
Mr Varadakumar added that his organisation, which has documented violence against Tamil people for 35 years, was "painfully aware of the murders, rape, disappearances and torture of the Tamil people" at the hands of the Special Task Force.
The widow's complaint references a series of letters from 1983 in which Sri Lankan diplomats asked the UK police for help with "commando operations training" for a police superintendent "who would be responsible for training and administration of a paramilitary unit to be set up here".
A Sri Lankan police officer of that rank then visited the RUC in Belfast.
The visit took place in the wake of six killings in Co Armagh by the RUC's Special Support Unit.
In November 1982 unarmed IRA members Gervaise McKerr, Sean Burns and Eugene Toman were shot dead in Craigavon.
Police fired 109 bullets into their car, in which no weapons were found.
Three RUC officers went on trial for murder but were acquitted, with the judge commending their "courage and determination for bringing the three dead men to justice".
Two weeks later Michael Tighe (17) was shot dead by police at a hay shed near Lurgan.
Another young man, Martin McCauley (19) - who would later come to prominence as a member of the Colombia Three - was seriously wounded.
Unarmed INLA men Roddy Carroll and Seamus Grew were shot dead by the RUC unit near Armagh in December 1982.
Former Deputy Chief Constable of Greater Manchester Police John Stalker - appointed to investigate the conduct of the RUC in the 1980s - compared the force's Special Support Unit in his biography to a "Central American assassination squad".
A Central Intelligence Agency report written around the time the Tamil complainant's family was killed was highly critical of Sri Lanka's Special Task Force (STF).
US intelligence staff were concerned that "a common STF tactic when fired upon while on patrol is to enter the nearest village and burn it to the ground".
The Police Ombudsman confirmed: "We have received a complaint relating to the actions of police officers in the 1980s, and this is now being considered."