Fifa have launched an investigation into the incident at Windsor Park on Saturday when assistant referee Stefan Wittberg was hit by a coin thrown from the crowd.

World football’s governing body are deciding whether to take disciplinary action after Wittberg needed treatment for a head wound during Northern Ireland’s World Cup qualifier against Poland.

The Swedish official was struck in the first half of the home side’s 3-2 victory, shortly after Poland had scored. The individual concerned was identified and ejected from the ground at half-time.

A Fifa spokesman said: “Fifa are currently reviewing an incident in the World Cup qualifier between Northern Ireland and Poland on Saturday, where a Swedish assistant referee was hit by a coin.

“Fifa has received a report from the match referee (Martin Hansson) as well as the match commissioner. Following a review of those two respective reports, Fifa will then decide on whether any disciplinary procedures will be opened.”

The Irish Football Association have already condemned the behaviour of the supporter who threw the missile.

“What happened was totally unacceptable,” said a spokesman. “The individual was identified and evicted from the stadium at half-time. Appropriate action will now be taken.

“But this was an isolated incident. The Northern Ireland fans were fantastic at Windsor and gave the team great vocal backing.”

Four men, meanwhile, are due in court in Belfast today in connection with the violent clashes between rival fans before and after the match.

The four — aged 30, 28, 26 and 22 — are all charged with disorderly behaviour linked to trouble at a city centre pub. The men were among nine people arrested during disturbances which left 11 police officers injured.

Rival fans fought with each other and clashed with riot police in sporadic confrontations across Belfast throughout the day.