The Defence Minister has lashed out at Russia for flying military planes through Irish-controlled airspace without permission.

Simon Coveney says it's "not acceptable" for foreign military planes to turn off their transponders to try and avoid detection.

He has admitted in the Dáil that Ireland only became aware of the presence of Russian planes last month when they were spotted by the UK.

However he says the planes only flew into international airspace controlled by Ireland - and not over Ireland itself.

"These aircraft did not enter Irish sovereign airspace at any time," Coveney said.

"The aircraft were in the area for which the Irish Aviation Authority has responsibility for the provision, operation and management of air navigation services for civil aviation,” he said.