Customs chiefs said officers were tipped off to a suspicious item on the shore near Liscannor in Co Clare, not far from the tourist hotspot of the Cliffs of Moher and other renowned surfing spots.

There was about 75kg of the drug inside the 6ft metal tube.

Small bales of cocaine, each about a foot long and weighing about 1kg, were found wrapped in plastic.

The Irish Republic's Revenue Customs Service described the tube as a "torpedo-type device" and said it may have been attached below the waterline of a cargo ship or another ocean-going vessel.

The seizure was made on Monday.

"It is not possible at this stage to say either where the drugs originated or their intended destination," a spokeswoman said.

Officials said the alarm was raised thanks to the customs drugs watch programme, which urges people living in coastal communities, maritime personnel and people living near airfields to report unusual or suspicious activities.

Investigations are continuing, a spokeswoman said.