Bomb disposal experts were called out three times overnight after separate explosive devices, two viable, were found in Dundalk and Dublin.
In Dundalk the army bomb disposal team made safe an improvised explosive device (IED) placed under a car outside a house on Castle Heights following a Garda request to attend the scene at 2:30am.
The IED as dismantled without the need for a controlled explosion and the all clear was given at 3.50am.
The same team then went to Glengowan, also in Dundalk, after a similar device exploded at a house earlier in the night. No damage or injuries resulted from the explosion and the all clear was given at 4.30am.
It is believed the devices were a warning from a criminal gang.
Meanwhile, in Dublin another device was found outside at house at Clonard Road in Crumlin. A team examined it between 10 and 11pm and subsequently declared it a hoax.
In all cases the remains of the IEDs were handed over to gardaí for ongoing investigations.