NAVAL sonar could have caused the deaths of whales that washed ashore in Co Donegal, it has been claimed.
The Irish Whale and Dolphin Group (IWDG) said multiple deaths reported in a single day was "highly unusual".
However, the Royal Navy last night said there was no evidence that the deaths had been attributed to any of its operations.
Three Cuvier's beaked whales were found dead on August 4 - one floating in Sheephaven Bay and one on Gola Island in Donegal, and another at Tirraun on the Mullet Peninsula in Mayo.
All three had likely been dead for several days and were in poor but similar condition, suggesting they died around the same time, the IWDG said.
There were two more Cuvier's strandings reported on Tuesday.
Cuvier's beaked whales are a deep diving species and have previously been found to be particularly affected by loud underwater man-made noise, such as sonar.
The group said it would be relatively normal to record three or four strandings in Ireland in any one year but unusual to have three in separate locations on one day.
Expert Dr Simon Berrow from the IWDG said such incidents were typically "associated with acoustic trauma linked to active sonar".
He said the Irish Navy did not have sonar capabilities but the Royal Navy did.
"When investigating these type of incidents, establishing if there has been sonar use is always the first port of call," Mr Berrow told the BBC.
"There is an exercise military zone to the west of Scotland, west of the outer Hebrides. If this event occurred in British waters, which it could easily have done, then these animals drifted towards the Irish coast."
A Royal Navy spokeswoman said there was no evidence that the deaths had been attributed to any Royal Navy Sonar operations, trials or exercises.
"We take our environmental responsibilities very seriously and continue to work with the relevant UK authorities to reduce any environmental risk," she said.
Between December 2014 and April 2015, 11 Cuvier's beaked whales were stranded on the Irish coast, around the same time that a similar number were recorded in western Scotland.
It was found that this coincided with naval manoeuvres at the time involving a search for an unidentified submarine, although the cause of death was not established.
Meanwhile, an investigation has begun into the killing of two peregrine falcons in Co Louth.
The birds of prey had established a nest in a remote location in the Cooley Mountains.
Three eggs and two dead adult falcons were recovered by National Parks and Wildlife Service staff from the site.
