A group of criminals supporting convicted rapist Christy Griffin paid a dissident republican based in Co Louth Euro2,500 each for the "highly sophisticated" devices.

Two of the pipe bombs have already been used and garda� now fear that several more have been sold to a gang in the west of the city.

A forensic examination of four recent pipe-bomb incidents around the capital has revealed that the devices were put together by the same bomb maker.

Two devices were discovered in the city centre, one in Finglas and one in Clondalkin. All have occurred over the last two months The engineer is a former provisional IRA member who defected to the Real IRA during the peace process. His devices are expertly constructed and have the ability to kill and maim.

Members of a gang supporting Christy Griffin, a 37-year-old who is serving a life sentence for the rape of his partner's child, made contact with the republican early this year and handed over around Euro20,000 for the 10 devices.

The feud between the Griffin gang and supporters of his victim has since subsided due to sustained garda attention and the group has been trying to get its money back by selling them on.

A drugs gang from Clondalkin is believed to have purchased several of the devices and garda� are extremely concerned.

A garda source said: "We knew that the Griffin gang had sourced some pipe bombs but we have now discovered that the exact number is 10 and that an experienced former provo bomb-maker was behind them.

"He has since aligned himself to the Real IRA and is now freelancing, selling these devices for between Euro2,000 and Euro2,500 a go.

"It was bad enough that one gang got the delivery but if they are being sold on that makes things far worse and far more difficult for us to track, especially since this bomb-maker is very skilled."

Senior garda� have been concerned about the increase in the number of pipe-bomb incidents. Previously most were crudely made but they have been increasing in quality over the last two years.

The warring gangs in Limerick now have access to pipe bombs which are sourced from Munsterbased former republican terrorists.

In April a viable pipe bomb was planted under a car in Clare but failed to explode. Garda� believe members of a west Dublin drugs gang was responsible for the "viable" device which was aimed at a man who had relocated to Clare from Tallaght.

Last week a senior garda was appointed by the garda commissioner to investigate the links between all pipe-bomb incidents over the last 12 months.

Detective superintendent Padraig Kennedy of Store Street garda station will scrutinise all forensic evidence taken from devices in a bid to determine how many people are constructing pipe bombs and who they are selling them to.

His investigation is expected to take a number of months.