A judge was targeted by republican dissidents and followed to the Belfast Boat Club on the shores of the river Lagan, sources have told the Sunday Tribune.

The security services are deeply concerned about the incident, which is the latest of several attempts by dissidents to target judges in the North in recent weeks. The threat is so severe that a special website has been set up to deal with the issue.

It is understood that judges will be able to log onto the website for advice. The existing general judicial site was regarded as unsafe for communication amidst fears that it could be compromised.

Security seminars are also being held for judges, teaching them how to spot home-made bombs which may be placed under their cars or attached to their premises, and how to respond if they find devices.

Another senior judge was forced to leave Belfast and move to north Down after a bomb was found near his home. That judge and the one followed to the boat club – whose names are known to the Sunday Tribune – have dealt with prominent dissident republican cases.

The threat is so substantial that the Sunday Tribune has been told that a lawyer from a nationalist background, considering taking up a judicial position, is rethinking their position.

In March, the Real IRA shot dead two British soldiers at Massereene and the Continuity IRA murdered Constable Stephen Carroll in Lurgan. A third dissident group, Óglaigh na héireann, is also active.

Sources also expressed concern that a laptop belonging to a senior judge, which has been stolen, could contain sensitive information. Last month, a judge had to flee a restaurant in Limavady, Co Derry, after dissidents followed him. He and his wife were alerted to the danger and left immediately.

The PSNI's heavily armed close protection unit – which provides security for politicians, judges and other VIPs – has been expanded to deal with the threat and 35 members of the police full-time reserve have been drafted in to give judges extra protection. For several days last month, sittings of many deputy crown court judges and other deputy district judges were cancelled due to the threat. Sources said the British lord chancellor, Lord Irvine, was being regularly briefed on the situation.

There is a sliding scale of protection for individual judges according to the likely paramilitary risk. Some have extensive security, while others have no protection.

There are now concerns that even low-level judicial figures, such as lay magistrates, could also be dissident targets.

With the peace process, judicial security has been decreased. Some judges believe the PSNI has wrongly minimised the risk they are facing from republicans.