Uniformed gardaí have been ordered to request armed back-up if they have any suspicions about emergency calls they are responding to over fears a simmering gang feud is to ignite.

Senior garda management, in an unprecedented move, have told armed detectives to back-up their uniformed colleagues before dealing with any callouts that could be linked to a criminal feud between the INLA and a major Crumlin-based drug dealer.

Last week, members of the INLA, led by murder suspect Declan 'Whacker' Duffy, carried out four separate attacks on members of a rival gang headed by 27-year-old 'Fat' Freddie Thompson.

Armed INLA members burst into a busy pub in Dublin's city centre looking for Thompson and produced a pistol in a bookmaker's shop where it was thought he was placing bets.

A close associate of Thompson was slashed in the face by Duffy while two other associates had three shots fired at their car.

Garda sources say there has not been as much tension in the city since November 2005 when three Crumlin gang members were murdered within 24 hours of each other.

The Sunday Tribune understands that both Duffy and Thompson are travelling in convoys of at least three vehicles with between six and 10 gang members accompanying them at all times.

Detectives say that there are a number of "spotters" travelling around Crumlin, Drimnagh and the north-inner city on motorbikes on the lookout for the rival convoys. These spotters are armed and ready to go to their associates at short notice to provide them with weapons.

The criminals travelling in convoy do not carry guns because they are stopped on sight when seen by gardaí.

The feud between Duffy and Thompson began when the INLA began to move in on the drugs territory traditionally controlled by the Thompson gang.

The INLA took a contract out on Thompson's life last December and since then he has escaped two assassination attempts.

After the second unsuccessful hit two months ago, Thompson's supporters decided that Duffy should be murdered and have vowed to kill him. Gardaí are taking the threats seriously and say it is only a matter of time before either an INLA member or one of Thompson's gang members are killed.

Both men have been warned by gardaí that their lives are in imminent danger but neither side is prepared to step back from the brink.

The INLA is now bigger than the IRA in Dublin and has been carrying out shootings, intimidation campaigns and pipe bomb attacks in a bid to drive out existing drugs gangs and take over their territory.

Gardaí say that the group is responsible for at least four murders over the last two years. The leader of the INLA's Dublin unit is 34-year-old Declan Duffy.