Ireland's embassy in Kyiv has ceased operating.
The ambassador and other staff have been moved to a secure location, as fighting continues in Ukraine.
However a dedicated helpline has been set up for Irish citizens in the country. They can contact it on +353-1-613-1700.
The Department of Foreign Affairs is advising against all travel to Ukraine.
All Irish citizens in Ukraine are advised to shelter in a secure place. However, citizens should consider leaving if they judge it safe to do sohttps://t.co/NJJACwWrL9
☎️The dedicated telephone line for emergency assistance for Irish citizens in Ukraine: + 353 1 6131700
— Irish Foreign Ministry (@dfatirl) February 24, 2022
But it says all Irish citizens in Ukraine should shelter in a secure place.
It says they should consider leaving "if they judge it safe to do so".
In a statement, the department adds: "It is likely that routes out of Ukraine will be severely disrupted and the road network and border crossings may face closures at short notice.
"Martial law has been declared in Ukraine. Citizens should closely monitor the advice of local authorities and reputable media sources."
It also notes that Ukraine's airspace is closed.
"If you believe you cannot leave safely, you should shelter in a secure place and monitor developments closely.
"Keep your situation and departure plans under constant review and ensure your travel documents are up to date.
"Bear in mind that communication lines (phone, internet) may be disrupted", it adds.
Additional reporting: Sean Defoe