Death threats have been issued to Sinn Fein members linked to the controversial appointment of an IRA killer to the role of ministerial adviser at Stormont, the party has announced.

The newly appointed adviser Mary McArdle, the minister herself Caral Ni Chuilin, north Belfast MLA Gerry Kelly and staff at the party's offices in the north of the city have all been threatened by a group calling themselves the Orange Volunteers.

Mr Kelly said a caller said bombs had been left outside his and Ms Ni Chuilin's homes, but that police have not found anything suspicious.

He said: "We've just received threats to our office in north Belfast which said there were bombs outside both Caral Ni Chuilin's home and my own, that there was a threat against the life of Mary McArdle and that they were going to kill people working in our office when they get the chance."

A police spokesman said: "We are taking these threats seriously and inquiries are ongoing."

Ms McArdle's appointment has whipped up a political furore, with the sister of her victim expressing disgust at the move.

Ms McArdle, 46, was jailed over the murder of primary school teacher Mary Travers and the attempted murder of her judge father Tom Travers in Belfast in April 1984 and subsequently released as part of the Good Friday peace agreement of 1998.

Ann Travers said she was sickened by the party's decision.

But Sinn Fein has defended hiring her as Ms Ni Chuilin's adviser, insisting that "ex-combatants" in the Troubles have a role to play in the peace process.

Ms Ni Chuilin said her adviser would be staying put and insisted the threats had not knocked Ms McArdle's determination to perform her new role. "I have every confidence in Mary McArdle and Sinn Fein will not allow ourselves to be intimidated either by direct threats or by people creating conditions in which these types of threats are made," she added.