Hugo Vandermersch scored a 79th-minute winner to shatter Larne's dreams of making more European history as St Gallen ran out 2-1 winners at Windsor Park.

After losses to Molde and Shamrock Rovers in the European Conference League, there was hope that Larne could collect a first point or win in Europe when Abdoulaye Diaby turned into his own net in the third minute.

The opener provided the loudest cheers of the night from the home support as the Larne players celebrated, but reality soon hit as the Swiss Super League side started to show their class.

St Gallen, who had a goal disallowed moments before Larne's opener, got a deserved equaliser when captain Lukas Gortler fired a superb volley beyond Rohan Ferguson in the 29th minute.

Larne, the first Irish Premiership team to reach this stage of European competition, held their own against the Swiss side but the decisive moment came with 11 minutes to play when Vandermersch smashed the ball home from close range after a counter attack.

It was a heartbreaking result for Larne, who remain bottom of the Conference League after three defeats, while St Gallen picked up their first win in this season's competition.

After a march through the streets of Belfast to the stadium before the game, St Gallen's vocal, 2,000-strong travelling support set the tone for a chaotic opening three minutes at Windsor Park.

The Swiss side thought they had taken the lead after 90 seconds when Hungary international Kevin Csoboth curled an effort into the corner after being played through by Chima Okoroji but the flag was raised for offside.

Moments later, Larne hit the front to spark wild celebrations with the St Gallen flares barely extinguished.

The Irish Premiership champions broke forward and Jordan McEneff looked to play through Andy Ryan, but defender Diaby stuck out a leg to divert the ball into his own net.

However, despite the celebrations, it was almost one-way traffic from there. Mihalio Stevanovic volleyed an effort straight at Ferguson, while Chadrac Akolo, Okoroji and Diaby all spurned half chances.

Ryan, ploughing a lone furrow up front, headed straight into the arms of keeper Lawrence Ati-Zigi in a rare Larne attack, but in the 29th minute the visitors were level.

Okoroji played in a teasing diagonal cross and captain Gortler fired a vicious volley back across goal from a narrow angle, which flew into the corner and left Ferguson stranded.

St Gallen continued to create half chances through Akolo and Bastien Toma, and Larne ended the half well as Cian Bolger headed across goal but could not find a red shirt shortly before the whistle.

The visitors, who had previously lost to Cercle Brugge and Fiorentina in Europe, had the first chance of the second half when Ferguson pushed away Akolo's low free-kick from the edge of the area.

Larne rallied and put in a sustained period of pressure, but just could not create the chance or land the key final ball.

Csoboth, always lively down the left, fired a shot that was well blocked by Bolger, though play was brought back for a handball.

There was a scare when Gortler clipped a ball forward for Willem Geubbels, who looked second favourite for the ball, but it was missed by the onrushing Ferguson. Thankfully for Larne, a combination of Ferguson and Bolger recovered the situation.

The decisive goal came when Gortler found Christian Witzig out wide and the substitute played a ball across goal for Vandersmersch to fire home, despite the best efforts of home defender Levi Ives.

The wild celebrations from the visiting players and staff said everything about how hard Larne had pushed them.

With the wind in their sails, captain Bolger had to be alert to hack away Gortler's cross before Diaby headed narrowly wide from a corner.

Substitute Moustapha Cisse thought he had added a third in stoppage time when he raced through, rounded Ferguson and tucked home but the flag was up for offside.

The substitute then forced Ferguson into a strong save as the visitors started to run the clock down.

Larne are without a win midway through their maiden European campaign, and face trips to Olimpija in Slovenia and Belarus club Dinamo Minsk, before a final home match with Gent.