Irish republican leader Gerry Adams, head of the Sinn Fein political party, is being questioned over the murder of a woman in 1972.
“Last month Gerry Adams said he was available to meet the PSNI (Police Service of Northern Ireland) about the Jean McConville case,” according to a Sinn Fein statement on the party’s website.
“That meeting is taking place this evening.”
Police confirmed a 65-year-old man presented himself to Antrim police station and was arrested.
McConville, a 37-year-old mother of 10, was snatched from her west Belfast flat and shot by republican paramilitaries, accused of passing information to the British army.
In 1999, the IRA admitted her murder and her remains were found on a beach in County Louth four years later.
Adams has always denied any involvement.
“I believe that the killing of Jean McConville and the secret burial of her body was wrong and a grievous injustice to her and her family,” he said.
“Well publicised, malicious allegations have been made against me. I reject these.
“While I have never disassociated myself from the IRA and I never will, I am innocent of any part in the abduction, killing or burial of Mrs McConville.”
Nobody has ever been found guilty of the murder, but former IRA leader Ivor Bell, 77, was last month charged with aiding and abetting based on an interview he reportedly gave to researchers at a US university.
The Boston College recordings were meant only to be made public after the deaths of the interviewees, but some content was handed over following a US court bid.
Adams, 65, says he was never an official member of the Provisional IRA. He has been president of Sinn Fein, the IRA’s former political wing, since 1983.
Opposed to British rule in Northern Ireland, the IRA carried out a campaign of violence during the three decades of sectarian bombings and shootings known as the Troubles.
The violence largely ended with peace accords in 1998 that paved the way to power sharing in Northern Ireland between largely Catholic republicans and mostly Protestant unionists favouring continued British rule.
The paramilitary group announced in 2005 that it was formally ending its armed campaign.