Irish Ryanair pilots are to strike for two days next week, their union said Wednesday, escalating an internal pay row at the budget airline.

Irish trade union Forsa said directly-employed pilots would strike for 48 hours from 12.01am on Thursday, August 22 - matching planned industrial action from British pilots.

A strike notice was served on Dublin headquartered Ryanair on Wednesday after mediation stalled earlier in the day.

A spokesman for Forsa - the parent union of the Irish Airline Pilots' Association (IALPA) - said the organisation submitted a detailed proposal in March "which sought pay levels and structures it says are in line with sector norms" as well as "proposals on pensions, working conditions and related matters."

"IALPA is seeking pay levels it believes are common and competitive in the commercial airline sector, from a company that made a substantial profit of €1 billion last year," said Forsa national secretary Angela Kirk.

"They tell me they feel forced into serving notice of potentially-disruptive industrial action by a company that seems either unwilling or unable to negotiate in a professional, transparent and constructive manner."

Last Wednesday members of the British Airline Pilots Association (BALPA) employed with the low-cost carrier voted 4-1 in favour of a strike with a 72% turnout.

BALPA's demands include "pensions; loss of license insurance; maternity benefits; allowances; and a fair, transparent, and consistent pay structure," it said in a statement."

British strikes will be held from August 22 to 23 and again from September 2 to 4 unless an agreement can be forged.

Forsa said notification of further industrial action days from their pilots will be given "in due course".

Ryanair has seen first-quarter net profits plunge by more than a fifth, as it faces rising costs, intense competition and Brexit turmoil, the Irish airline said on July 29.

Performance was also hit by pan-European strikes last year that forced it to cancel flights, affecting thousands of passengers, and offer improved pay to staff via landmark union deals.