A secret Irish government memo has warned of "conflict at sea" and "blockades" in the Republic's waters in the immediate aftermath of a no-deal Brexit.
Dublin ministers were given the dire warning as part of a confidential briefing from Tanaiste Simon Coveney.
It is understood the memorandum also outlined how disruption at Dublin Port could undermine public confidence in the security of food and medicine supplies in the Republic and lead to panic buying.
Mr Coveney's briefing to cabinet contained some of the starkest warnings to date on the consequences of a no-deal Brexit.
Ministers were informed last week that a failure to ensure the Republic has sufficient measures in place to assure the European Commission and other EU members that the bloc's single market is being protected would put the state's own single market membership at risk, "with serious economic consequences" as a result.
The starkest warning related to areas that fall outside the control of the Irish government, including the loss of access to UK fishing zones.
This could create a possible displacement of fleets of ships from other EU member states who normally use waters around the UK and raises the potential for "conflict at sea and blockades", the memo said.
The report, compiled by civil servants, highlighted the potential for trouble at sea to seriously escalate at an early stage after October 31 and have a significant impact on the Irish fishing industry.
There were further warnings of the risk of significant delays and traffic disruption at Dublin Port - which could have knock-on effects for traffic outside the port - in the immediate period after Halloween. Disruption is likely due to trucks arriving at the ports with incomplete or no documentation, ministers were informed.
They were also given details of other factors outside the Irish government's control, including possible decisions taken by UK and EU ports, ferry companies and protests by fishermen - all of which could cause delays.
Ministers were informed that disruption at Dublin Port or on the UK landbridge - which is how much of Irish freight accesses mainland Europe and vice versa - could "undermine public confidence in the security of supply lines, in particular food and medicines", with the consequent risk of consumers panic buying and stockpiles being depleted.
The cabinet was informed that risks remain both from the loss of public confidence and a lack of preparedness by businesses for a no-deal scenario.