In a fairly even opening half Ireland fell behind in stoppage through a Paul-Friedrich Koller penalty which came about following a counter attack from an Irish corner.
In the second half Ireland were undone by three set-pieces. SK Rapid’s Deniz Pahlivan made it 2-0 before Koller completed his hat-trick with a second-half brace.
Ireland will face Sweden on Saturday with their final game coming on Monday against Norway.
Republic of Ireland: Jimmy Corcoran (GK), Sean McEvoy, James Furlong, Andrew Ombamidele, Brandon Holt, Seamus Keogh (C), Conor Carty, Jaden Charles, Charlie McCann, Tim Sobowale, Alex Dunne.
Substitutes: Harry Halway (GK), Nico Jones, Tony Springett, Josh Giurgi, Sean Kennedy, Luke Turner, Kian Leavy, Gabriel Adebambo, Cole Kiernan.
Austria: Nikolas Polser (GK), Paul-Friedrich Koller, Nicolas Zdichynec, Matthias Braunoder (C), Nicolas Binder, Sefik Abali, Pierre Nagler, Benjamin Bockle, Luca Kronberger, Manuel Polster, Kevin Sostarits.
Substitutes: Felix Kochl, Simon Nelson Nosa Salami, Mako Dijakovic, Gabriel Zirngast, Deniz Pahlivan, Stefan Radulovic, Edin Mujkanovic, Bernhard Zimmermann, Philipp Jorganovic
Republic of Ireland Under-18 squad
Goalkeepers: Jimmy Corcoran (Preston North End), Harry Halwax (Derby County)
Defenders: Alex Dunne (Shamrock Rovers), Andrew Omobamidele (Norwich City), Jaden Charles (Derby County), James Furlong (Brighton & Hove Albion), Luke Turner (Aberdeen), Sean McEvoy (Ballinamallard), Nico Jones (Oxford United), Timi Sobowale (Manchester City)
Midfielders: Brandon Holt (St Patrick’s Athletic), Gabriel Adebambo (Dundalk), Kian Leavy (Reading), Seamas Keogh (Southampton), Tony Springett (Norwich City) Sean Kennedy (Cork City), Charlie McCann (Manchester United)
Forwards: Conor Carty (Wolverhampton Wanderers), Cole Kiernan (Sunderland), Josh Giurgi (Norwich City)
5 September: Ireland 0-4 Austria
7 September: Sweden v Republic of Ireland, KO 15:00 (Irish Time), Kubikenborgs IP
9 September: Republic of Ireland v Norway, KO 16:30 (Irish Time),Thulevallen