Helen McKendry, eldest daughter of murdered IRA victim Jean McConville, holds a photo showing her mother (left), herself (second right) and members of their family at her home in Northern Ireland on Saturday. Photo: AFP

Northern Ireland police extended the detention of Sinn Fein leader Gerry Adams by two days on Friday to give detectives more time to question him about a 1972 murder, raising the stakes in a case that has rocked the British province.

Adams' arrest over the killing of Jean McConville was among the most significant in Northern Ireland since a 1998 deal ended decades of tit-for-tat killings between Irish Catholic nationalists and mostly Protestant pro-British loyalists.

Northern Ireland Deputy First Minister Martin McGuinness, a Sinn Fein member and close Adams ally, said the decision by the Police Service of Northern Ireland (PSNI) to seek an extension confirmed his view that the arrest was politically motivated.

"There is a cabal in the PSNI that have an agenda, a negative and destructive agenda to both the peace process and to Sinn Fein," McGuinness told a news conference in Belfast. Northern Ireland's justice minister denied the accusation.

"I believe Gerry Adams will be totally and absolutely exonerated and I believe that Gerry Adams will continue to lead this party," said McGuinness, a former Irish Republican Army (IRA) commander who only last month met Queen Elizabeth in a sign of normalized ties between Britain and Ireland since the peace pact.

The decision extends Adams' detention at a police station about 25 kilometers northwest of Belfast until 1900 GMT on Sunday. Adams, who led the IRA's political wing in the 1980s and 1990s, must then be freed or charged unless police can convince a judge to agree to an additional extension.

Reuters