Within the space of five days last weekend, two major crimes took place that have raised questions about the power, influence and ambitions of the Real IRA and the former members of the Provisional IRA in the south.

On Friday last, Jason Egan (23) was shot dead in Mulhuddart, west Dublin, by a lone gunman.

Gardaí believe he was killed because he is a relative of the prime suspect in the killing of Wayne Doherty (32), a boxer previously associated with the IRA, who was shot dead in Blanchardstown three months ago.

In the aftermath of this killing, former members of the disbanded Provisional IRA swore revenge for Doherty's killing. Since they couldn't locate Egan's relative, believed to be living in Turkey, they killed him instead.

Following Doherty's murder, a notice appeared in the republican newspaper, An Phoblacht, in which "the Republican Movement Dublin" offered condolences for his death. Dozens of uniformed men carried Doherty's tricolour-draped coffin at his funeral to the music of a lone tin-whistler.

It was a very public show of power by the Provos and shows that they have not disappeared into the shadows completely.

The Provisional IRA has been overtaken by dissident groups, in particular the Real IRA.

Four days after Egan's murder, the Real IRA was linked to the largest ever haul of contraband cigarettes in Europe.

Nine people were arrested after a ship containing 12 million cigarettes, worth €50m, was seized in Co Louth following a lengthy surveillance operation.

The operation, codenamed 'Samhna,' targeted crime gangs operating on both sides of the border, including the Real IRA.

A senior source said speculation that the entire haul was destined for the dissident paramilitaries was incorrect. While the dissident paramilitaries have extensive experience with smuggling, it was not the only criminal gang involved in the international ­operation.

But this is just the latest in a series of activities the Real IRA has been involved in that has caused serious concern among special branch gardaí.

"Of all the dissident groups, the Real IRA are, without any doubt, the biggest threat to security. And they do pose a very real threat," said the source.

The group occasionally works in collaboration with the other splinter dissident group, the Continuity IRA.

This group has suffered repeated splits caused by leadership struggles and its active members across Ireland number between 20 and 30.

Because of internal strife, some of its members have defected to the Real IRA, regarded as far stronger and better organised.

The INLA is the third dissident group causing problems in the south.

A senior detective said that a series of convictions against its members has seriously curtailed its activities. Over the past 12 months, over 20 members of the INLA have been convicted by gardaí for membership of the organisation and other crimes.

Before this, there were serious concerns about their increasing foothold, particularly in working-class areas of Dublin.

"At the moment, the INLA are at the bottom of the pile in relation to political as well as subversive activities. A series of convictions has been putting them out of business," said the source.

Considered "the biggest thugs" of all dissident groups, the INLA never made a secret of its involvement in drug-dealing and one of its controversial Dublin leaders Declan 'Whacker' Duffy, was involved in a high-profile falling out with a Crumlin gang led by 'Fat' Freddie Thompson but it officially disbanded last month and is expected to effectively disappear.

Splinter Groups: From armed struggle to crime and drugs

Real IRA

The most influential of hardline splinter groups, its membership is growing in the south and gardaí are increasingly concerned about their activities. It has about 100 active members in Tallaght, Dundalk and Belfast. It raises funds for planned bombings primarily through cigarette and diesel smuggling and, in more recent years, by providing security at nightclubs and pubs. One if its leaders is Michael Campbell, who is facing trial in Lithuania for trying to buy arms and explosives.

Continuity IRA

The CIRA has far less support than the Real IRA, with up to 30 active members. The group has been split in recent months by leadership struggles and has lost some members to the Real IRA. The two groups often work together, particularly in cross-border smuggling operations. Both the CIRA and the Real IRA claim to be anti-drugs to garner support in communities but many of their members have been involved in drug-dealing in the south.

INLA

Support for the INLA in the south was growing at an alarming pace 12 months ago but gardaí are satisfied it has now majorly curtailed its activities following several high-profile convictions at the Special Criminal Court. One of the deadliest and most ruthless paramilitary groups in the Northern conflict, the INLA announced last month it was preparing to disband. A spokesman for Irish Republican Socialist Party (IRSP) Dublin Cumann, the INLA's political wing, told the Sunday Tribune: "I fully support and am behind the statement. Our new political direction should be applauded and endorsed by all."

Provisional IRA

The Independent Monitoring Commission (IMC) has found that the PIRA has brought its "armed struggle" to an end. Despite this, former members have been "trading on their former notoriety" in the south. Gardaí believe former members are behind last Friday week's killing of Dublin man Jason Egan in a retaliation attack for a previous murder.

However, the men suspected of carrying out the murder were acting in isolation and not on orders. "It's as simple as this, the Provisional IRA are not a threat anymore as an organised group but individuals are still potentially very dangerous," said a garda source.