Amnesty International has written to the Northern Ireland Secretary expressing serious concerns about police legal action to force a journalist to hand over information about the Real IRA claim of responsibility for the murder of two soldiers.

Amnesty said today it highlighted to Shaun Woodward the very real possibility of the freedom of the press, and investigative journalism in particular, being put at risk.

Suzanne Breen, northern editor of the Dublin-published Sunday Tribune, received the Real IRA claim of responsibility for the murders of Sappers Mark Quinsey, 23, from Birmingham, and Patrick Azimkar, 21, from London, who were shot dead at the gates of Massereene barracks in Antrim in March.

Prominent dissident republican Colin Duffy, 41, from Lurgan, Co Armagh, has been charged with the double murder and police are still looking for other suspects.

The Police Service of Northern Ireland want Ms Breen to hand over materials including notes of her conversations with the Real IRA caller.

Last month Belfast Recorder Tom Burgess sat in private to hear from police why they wanted Ms Breen's notes - but she and her legal team were excluded from hearing the police evidence.

Ms Breen is refusing to hand over anything and is due back in court tomorrow when her lawyers will argue her case.

Patrick Corrigan, Amnesty's Northern Ireland director, said: "There are real concerns here about possible violation of Suzanne Breen's human rights.

"By using anti-terrorism legislation and the use of secret evidence, the Government has deprived her of the right to challenge evidence used against her.

"That is an affront to natural justice and international human rights standards."

He said that on the few occasions when such secrecy might be justified, an independent party should make any decision to keep evidence confidential.

"That basic standard has not been met here and consequently Ms Breen's right to a fair and public legal process is in serious jeopardy."

Colm O'Gorman, executive director of Amnesty International Ireland, said: "We have reminded the Secretary of State that freedom of the press is a vital part of the right to freedom of expression, guaranteed by international human rights law.

"The failure to defend the right of journalists to protect their sources undermines investigative journalism and the public interest."

The UN had recommended that journalists should only be obliged to reveal sources in exceptional circumstances, where there was no other way of obtaining information and where the public interest clearly overrode the importance of protecting sources, he said.

"It is doubtful that this test has been satisfied in this case.

"Simply put, journalists should not be used as an alternative to proper policing and intelligence-gathering."