Nine men accused of murder in the biggest trial of suspected militants in Northern Ireland for more than 20 years were acquitted Wednesday after a judge branded the prosecution's so-called chief supergrass witnesses as liars.

Fourteen suspected members of banned militant group the Ulster Volunteer Force (UVF) had been on trial, facing a total of 97 charges mainly linked to the murder of the head of rival group the Ulster Defence Association (UDA).

With armed police both inside and outside the courtroom, there was muted applause from the packed public gallery and loud cheering from supporters outside when the bulk of the accused walked free.

The charges were based on the evidence of suspected UVF members, brothers Robert and Ian Stewart, who had served three and a 1/2 years for aiding and abetting the murder but got reduced jail terms in return for testifying against their alleged former colleagues.

However Justice John Gillen told the court their testimonies were infected with lies.

These are witnesses of very bad character who have lied to the police and to the court, on some occasions wrongly implicated a number of men who were clearly not present at the crimes suggested, Gillen, who sat without a jury, said.

A large number of such so-called supergrasses - informers used to give evidence against former associates - were used in Northern Ireland in the 1980s to convict hundreds of pro-British and Irish nationalist suspects.

But the system was largely discredited after most of the defendants were freed on appeal.

UDA chief Tommy English was gunned down at his home on the northern outskirts of Belfast in October 2000 during a feud between the UDA and the UVF which claimed seven lives.

Of the five charged with lesser offences in the case, one man was found guilty of possessing items intended for terrorism.

Street violence by pro-British militants has increased in the past year amid frustration about a 1998 peace deal that largely ended 30 years of conflict that killed some 3,600 people. Police have said Irish nationalist militants opposed to the deal are more dangerous than at any time since 1998.

The 1998 agreement paved the way for a power-sharing government bringing together Protestant loyalists who want Northern Ireland to remain part of the United Kingdom, and Irish nationalists who want it to be part of a united Ireland.

(Editing by Padraic Halpin)