The Defence Forces have deployed a number of units to assist fire crews battling gorse fires in the northwest of the country.
Areas of Donegal, Galway and Mayo have been affected by the blazes which have threatened homes in some places.
Fires are also being tended to on the Mourne Mountains in Co Down.
The Doochary, Lettermacaward and Dungloe areas of Donegal have been worst affected. Local authorities believe they were started deliberately.
Gorse fires have also been reported in forest and bog areas of Connemara in Galway and Pontoon in Mayo.
There are no reports of injuries at this stage.
A Defence Forces spokesman said troops, aircraft and equipment were deployed to battle the fires in response to a request from local authorities.
An Air Corps helicopter fitted with a 1,200 litre water bucket was used to drop water on fires in the Dungloe area. A second helicopter is preparing to drop water on fires in Foxford and Pontoon in Mayo.
Another helicopter with a fire safety qualified Army engineer on-board is providing advice and information to the fire fighting effort on the ground in Co Mayo and Co Donegal.
Some 50 troops with specialist fire-fighting suits have travelled to Dungloe and parts of Mayo with further troops placed on standby to be deployed if required.
Meanwhile, PSNI officers and fire fighters are attempting to quash fires in the Mourne Mountains.
It is understood the fires were started by an arsonist. Hill walkers and holiday-makers have been advised to avoid the area over the coming days.
Northern Ireland's chief fire officer Peter Craig told the BBC that 40 foott high flames were a feature of the blaze. He warned that the fires could spread faster than people could run.
He said of the arsonists: "The key issue is they need to know their actions have consequences. People out in the mountains enjoying the day are coming down facing a ferocious fire. One moment of what they consider fun could end in a tragedy."
Additional reporting: PA