An Irish Republican Army suspect was charged Wednesday with murdering a British Army intelligence agent on the Northern Ireland border 32 years ago, a surprising turn in one of the conflict's most mysterious unsolved killings.

Northern Ireland state prosecutors levied the unexpected new charge at a regular bail hearing for Kevin Crilly. Last year the 58-year-old was arrested and charged with kidnapping and falsely imprisoning — but not killing — Capt. Robert Nairac.

In May 1977 an IRA gang abducted Nairac from a pub in the outlaws' border stronghold of South Armagh, a close-knit society dubbed "bandit country" that Nairac had sought to infiltrate by posing as a Belfast IRA man.

The Oxford University-educated Catholic had learned Gaelic IRA drinking songs and used them in his pub-crawling surveillance operations. But it didn't fool local IRA men. His body was never found, and rumors have persisted that it was butchered in a factory meat processor.

Prosecutors did not reveal why they had increased the charges against Crilly to murder. Crilly's lawyers complained bitterly they had been ambushed by the move as well as by a renewed attempt to withdraw Crilly's right to bail.

District Judge Austin Kennedy, at the hearing in the border town of Newry, ordered Crilly kept in police custody while prosecutors pursued an appeal against his bail at a higher court in Belfast.

Prosecutors said they feared Crilly would flee to the neighboring Republic of Ireland or further afield because of the murder charge. His defense attorneys said that was nonsense and cited his regular check-ins with police since winning bail following his May 2008 arrest.

Six IRA members have already served prison sentences for their part in overpowering Nairac, taking him across the border into a Republic of Ireland forest, interrogating him and shooting him in the head.

Belfast media investigations — including a 2007 BBC documentary that filmed Crilly using a concealed camera and microphone — have identified him as the IRA driver that night.

Crilly admitted in court last year that he drove one of the IRA men to the scene of Nairac's torture. Police have testified they found traces of Nairac's hair in Crilly's car.

Crilly fled to the United States following Nairac's killing but returned following Northern Ireland's 1998 peace accord. That pact offered early paroles for IRA convicts and a de-facto amnesty for any IRA members subsequently convicted of pre-1998 crimes.

That peace offering means Crilly, if convicted, could expect parole within months.

Nairac posthumously won the George Cross, Britain's highest civilian award for bravery. His 1979 citation credited him with exceptional toughness and bravery for trying repeatedly to escape, and refusing to reveal anything to his executioners.

But several well-placed British intelligence agents and army commanders at the time have described Nairac as reckless and even out of control.

The IRA killed more than 700 British soldiers during its failed 1970-97 campaign to force Northern Ireland out of the United Kingdom. Nairac was the only one who disappeared.