Britain's Channel 4 News said it had "exclusive proof that successive British governments covered up the full story of Bloody Sunday for a generation" and an Irish writer said new evidence pointed to previously undisclosed army gunfire.

"I would like to see the case reopened, that is the first priority," said John Kelly, whose brother Michael was a victim of one of the British region's most controversial episodes when paratroopers opened fire at an Irish nationalist rally.

An official inquiry headed by Lord Widgery, Lord Chief Justice, exonerated troops saying that they had come under fire.

But Catholics opposed to British rule have always dismissed the findings. They say the casualties were unarmed victims of deliberating shootings on Sunday, January 30 1972.

"Murder was committed that day in the name of the British government," Kelly, chairman of a families' Bloody Sunday Justice Campaign, told Reuters.

He was speaking ahead of a report that Channel 4 News said was based on audio tapes of military radio messages "suppressed since the official inquiry," which refused to accept them as evidence because they had been illegally obtained.

The programme will be aired on Friday night ahead of the 25th anniversary of Bloody Sunday and against a background of renewed violence by Catholic-backed Irish Republican Army (IRA) guerrillas and threats that their Protestant "loyalist" foes will avenge it.

"Recorded by a radio ham, the tapes prove that soldiers other than the Parachute Regiment were positioned along the old City Walls of Londonderry and indicate that these men fired and hit civilians," the television news organisation said.

"Channel 4 News has obtained post mortem evidence which shows that at least three unarmed men were killed by bullets fired down through their bodies from above.

"The City Walls are located high above the Bogside area where people were killed and are in direct line of sight to where the three men fell."

A separate investigation by an Irish human rights activist, Don Mullan, who studied many of the original first-hand accounts, turned up a similar finding.

He uncovered almost 50 statements from people who said soldiers were positioned on the walls and many were "very clear that firing was coming" from that vicinity, he told Reuters.

Mullan, whose "Eyewitness Bloody Sunday" is published on Saturday, said: "Widgery confines himself to...the 108 rounds allegedly fired by paratroopers at ground level. He did not deal with the role of the British army on the walls."

Three of victims had been hit from a 45 degree angle. Mullan said that from the statements and autopsy reports, an independent ballistic expert, Robert Breglio, who had spent 25 years with the New York City Police Department, had concluded that they were likely to have been "hit by a single marksman using a telescopic sight operating from a height."

"I think that the case must be reopened because we have always known that these people wre murdered. We have raised enough suspicion... to warrant an investigation, especially into these three, and preferably into all 13 killed that day," Mullan said.

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