A 69-year-old man has been arrested in connection with the McGurk's Bar bombing which claimed the lives of 15 people in one of the worst mass killings of the Troubles.
The man was arrested in Co Antrim yesterday and taken to Antrim PSNI station for questioning.
The pub bombing was carried in december 1971 by a UVF team who placed a bomb at the door.
The RUC later gave false information claiming that the bomb had been left inside the bar by the Ira.
In February 2011, the Police ombudsman said the original RUC investigation into the bombing was "biased".
last month, an east Belfast loyalist was arrested in connection with the attack but later released without charge.
The only person convicted in relation to the attack, getaway drive Robert Campbell, died last year.
Ken Wilkinson from the Progressive Unionist Party, which is linked to the UVF, last night accused authorities of concentrating on historical incidents involving loyalists.
"It's two-tier justice and republicans on the ground are a protected species," he said.
"It's not about justice, it's about the levels of justice. I have challenged David Ford about the two-tier system, there can't be a protected species."