The Irish embassy in Russia has requested consular access to a man detained in Moscow after being accused of spying.
It has emerged that Paul Whelan who was detained on December 28 holds Irish, UK and US citizenship.
Russian news agency TASS has reported that a criminal investigation has been opened against the 48-year-old on espionage charges.
He could face between 10 and 20 years in jail if found guilty.
In a statement, the Department of Foreign Affairs says it will provide all possible and appropriate assistance in relation to the case.