Slovenian international Dare Vrsic scored twice -- from a penalty and controversial, if stunningly executed, free-kick -- to leave Bohemians with a difficult night ahead of them in the second leg of their Europa League second round qualifier at Dalymount Park next week.
"I'm disappointed, because when you don't concede from play you have to think your gameplan's been quite good," said Bohemians manager Pat Fenlon after the game.
"I thought both decisions, for the penalty and the free-kick, were very, very dubious -- particularly the free-kick.
"The penalty was hard for me to see and the free-kick was a great tackle from Owen (Heary). The player fell into him. To concede two from set-pieces is more disappointing than anything. If they'd scored two or three from play, you'd say fair enough."
Roared on by their raucous support, Olimpija enjoyed all the possession as Bohemians were on the back foot from the off. A couple of early scares that were off target were followed on nine minutes by right-winger Matic Fink rattling Barry Murphy's crossbar from 20 yards.
Another let-off for Bohemians arrived on 26 minutes. Davor Skerjanc got to the end line to pull a perfect ball back across the face of the goal, but Anej Lovrecic contrived to knee his effort over the bar from just yards out.
Then, just as Bohemians looked to be holding out for the interval, it went pear-shaped in first-half stoppage time.
First, captain Heary somehow cleared the ball off the line to deny Skerjanc. Seconds later Murphy clattered into the back of home skipper Dalibor Radujko as he came for Lovrecic's dinked cross into the area.
Portuguese referee Carlos Xistra didn't hesitate in pointing to the spot and, though Murphy dived correctly to his left, Vrsic's spot kick powered into the corner of the net.
Olimpija remained well on top and got their second, perhaps killer goal, on 76 minutes.
Bohemians felt that Fink tripped himself on the edge of the area but, despite their protests, Vrsic's brilliant free-kick went in off the underside of the bar.
"The heat was sapping and the work rate from the players was incredible," said Fenlon in praise of his players. "I don't think anyone could realise how warm it was out there.
"They are good players," he said of Olimpija. "They moved the ball well and they had good movement. But I thought we coped okay. We soaked up a lot of pressure and I can't remember when they played little one-twos and got in behind us. I thought they got frustrated up to the goal, the penalty.
"It will be difficult," added Fenlon on the prospects for the return. "We've got to score the first goal and see how they react, do they panic a little bit.
"It's about scoring the first goal. They are a good side and we'll have our work cut out.
Olimpija Ljubljana -- Dzafic; Jovic, Sretenovic, Andelkovic, Bozic; Lovrecic (Ranic 54), Radujko; Fink (Cadikovski 76 ), Vrsic, Skerjanc (Omladic, h-t); Valencic.
Bohemians -- Murphy; Heary, Burns, Price, Cahill; O'Brien; Buckley, Cronin (Rossiter 87), Bayly (Traynor 64), Brenann; Fagan (Flood 62 )
Ref -- C Xistra (Portugal)
•Fulham avoided embarrassment in Northern Ireland last night but were made to fight all the way for a 3-1 victory over Crusaders in their Europa League second qualifying round tie.
Martin Jol's men took the lead on 39 minutes through a Matthew Briggs thunderbolt, but the spirited hosts stunned their Premier League opponents nine minutes into the second half when Timmy Adamson levelled with an excellent finish.
Crusaders scrapped manfully but they ran out of steam, with Bobby Zamora's 74th-minute header edging the visitors ahead and a Danny Murphy penalty three minutes later leaving them in control.