Relatives of people killed during the Troubles have called for the activities of the UDR in east Tyrone to be investigated.
The call comes after an Irish News investigation revealed that a deadly assault rifle was used by loyalists to kill up to 12 people between 1988 and 1994.
The deadly Czech-made VZ58, one of hundreds believed to have been smuggled into the north with the help of British intelligence, was also used in the attempted murder of two people.
Details of the gun, which had the serial number R18837, emerged during an inquest into the 1994 murder of pensioner Roseanne Mallon - it's final victim.
The majority of attacks using the gun have been directly linked to the UVF.
It is also suspected that some members of the UDR based in Co Tyrone were involved in a sustained sectarian campaign carried out in the area at the time.
The Czech-made weapon was one of two VZ58s used to kill four men - three of them IRA members - at Boyle’s Bar in Cappagh, Co Tyrone, on March 3 1991.
Relatives of Malcolm Nugent (20), Dwayne O’Donnell (17) and John Quinn (23) and civilian Thomas Armstrong (52) marked the 30th anniversary of their deaths last week.
A Historical Enquiries Team (HET) report into the killing of Mr O'Donnell, released by the PSNI last year, revealed that three part-time UDR members were among four suspects arrested in December 1991.
The arrests took place after a joint British army and RUC review undertaken "as a result of raised concerns of security service collusion in east Tyrone".
An examination of intelligence relating to several murders and attempted murders between 1988 and 1991 "highlighted concerns in relation to several members of 8 UDR" - which covered parts of Co Tyrone.
The HET report said intelligence was received naming three soldiers as being responsible for Mr O’Donnell’s murder.
It also claimed the UDR men “were also named as responsible for other murders”.
Three UDR men were also questioned in relation to the killing of Sinn Féin member Tommy Casey near Cooksktown in 1990.
Briege O’Donnell, mother of Dwayne O’Donnell, last night said: "Given the new information revealed in our HET report and the weapons linkages, it is paramount that the involvement of the UDR and other agents of the states are fully investigated as part of this independent investigation."
Ms O'Donnell said previous RUC investigations "failed to carry out fair and proper investigations".
Mark Thompson from Relatives for Justice said people related to republicans were often targeted by loyalist gangs.
“Far from thwarting the activities of loyalism, which is routinely cited, this period saw a new phase of a state policy of using loyalism to target republicans and terrorize nationalists," he said.
