The Tánaiste has told the Dáil that a US military airplane armed with a fixed weapon landed at Shannon Airport this year, in breach of normal rules.

Eamon Gilmore says the case has been raised at the highest possible level with the US Embassy.

366 foreign military aircraft landed at Shannon in the first nine months of the year, but they are subject to certain conditions, including that no arms are carried on board and that the flights don't form part of military exercises or operations.

However, in a written answer to Galway West TD Derek Nolan, Eamon Gilmore has revealed that the Department of Foreign Affairs is aware of one instance this year when a US flight carrying a fixed weapon landed at Clare's international airport, breaching normal conditions.

The government raised the incident with the US embassy - officials there have said it was an isolated incident that took place because of an administrative error, and that steps have been taken to ensure it won't happen again.