Ireland's goalkeeper Shay Given reacts on the ground after Croatia scored their third goal during their Group C Euro 2012 soccer match at the City stadium in Poznan, June 10, 2012. [Photo/Agencies]

POZNAN, Poland - Croatia took the initiative in the Euro 2012 Group C after two goals from Mario Mandzukic helped them to a 3-1 victory over Ireland here on Sunday.

Mandzukic struck in the early stages of the first and second half, with his two headers firing Slaven Bilic's side above Spain and Italy to the top of the group.

Mandzukic, the man of the match, angled his body impressively to beat Shay Given only three minutes into the game, but Ireland's Sean St. Ledger levelled the score with a header from Aiden McGeady's free-kick.

But Giovanni Trapattoni's team suffered a bitter blow before half-time as Everton striker Nikica Jelavic netted from what appeared to be an offside position. Mandzukic added a third shortly after the interval after his effort struck the post and went in off Shay Given.

Croatia's Nikica Jelavic (R) scores a goal past Ireland's goalkeeper Shay Given during their Group C Euro 2012 soccer match at the City stadium in Poznan, June 10, 2012. [Photo/Agencies]

Ireland's defeat, just the third competitive reverse during Trapattoni's four-year tenure and the first on foreign soil, means the team heads into Thursday night's showdown with Spain, reigning world and European champions, knowing their hopes of qualification could effectively be over if they do not come away with at least a point.

Ireland emerged from the tunnel before kick-off to be greeted by a sea of green and a torrent of noise as they embarked upon their first game at the European Championship finals for 24 years.

Bilic's men scented victory as Mandzukic and strike-partner Jelavic repeatedly stretched Richard Dunne and St Ledger at the heart of Ireland's defence, the signs were ominous.

Full-backs Srna and Ivan Strinic repeatedly made their way forward to occupy wingers Aiden McGeady and Damien Duff in areas of the pitch where they would rather not have been, and with Luka Modric starting to pull the strings in the middle of the field, Ireland were desperately in need of inspiration.

This was the first time Ireland conceded three goals in a match at a major international finals. They had previously gone 17 games without doing so.

Ireland fans sit dejected in the stands after their teams defeat to Croatia in the Group C Euro 2012 soccer match at the city stadium in Poznan, June 10, 2012. [Photo/Agencies]