During an international friendly match against Switzerland in March this year, the Republic of Ireland's players had the years 1916 and 2016 embroidered on their shirts.

The Easter Rising took place in April 1916, where a group of rebels sought to end British rule in Ireland and establish an independent Irish Republic.

Fifteen of the rebellion leaders were later killed while around 485 people lost their lives across six days of conflict.

The news follows the ongoing debate regarding the use of poppies on shirts for the upcoming World Cup qualifier between England and Scotland on November 11 - also Remembrance Day.

It is not clear what the sanction will be for the FAI if it is found to have breached FIFA’s laws on political symbols.

A FIFA spokeswoman confirmed proceedings had been opened against the FAI, adding: "We cannot comment further at this stage nor speculate on any outcome."

FIFA strictly bans political, religious or commercial messages on match shirts.

The football associations of England and Scotland, however, have claimed they will defy FIFA and allow their players to wear armbands with poppy emblems when the two neighbours collide at Wembley Stadium in London.

Prime Minister Theresa May has supported this position, saying: "A clear message is going out from this House. 

"We want our players to be able to wear those poppies.

"Our football players want to recognise and respect those who have given their lives for our safety and security.

"It is absolutely right they should be able to do so."

FIFA issued a number of fines yesterday to ten international football associations after they were found guilty of "discriminatory and severe unsporting conduct by spectators as well as religious manifestations".

One country punished was Iran, who were fined CHF 45,000 ($46,100/£37,100/€41,500) for several "religiously motivated displays" during a match.