The company also braced those located in Belfast to expect an announcement soon.
This also follows on from the recent move by SSE Airtricity to hike its prices by 22%.
Sinn Féin MLA Caoimhe Archibald has expressed concerns over the rising gas prices and labelled the latest announcement another "huge blow for already hard-pressed families".
"Many families, workers and pensioners here are still reeling from the British Government's attack on their livelihoods by increasing national Insurance contributions, ditching pension protections and cutting Universal Credit and Working Tax Credit," MLA Archibald said.
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"They simply will not be able to absorb these additional costs and there is no doubt that more households will be pushed into poverty as a result.
"It is particularly concerning given that it comes as we enter winter when the demand for gas will significantly increase.
"I have written to the utility regulator highlighting my concern on the scale of these increases and urging him to ensure energy companies are doing everything they can to cut the costs passed on to customers.
"Just like the British Government's attack on workers, pensioners and families, these hikes in energy costs will hit hardest on those already least able to afford it."
