The first shock of the Olympics has been delivered when Japan edged out Spain 1-0 in the opening game for both countries.

Yuki Otsu's goal in the 34th minute was all Japan needed against the highly touted Spanish squad.

Spain was shorthanded after Inigo Martinez's ejection four minutes before the half and the Spanish couldn't recover. Martinez received a red card for a trying to stop Japan's Kensuke Nagai.

"It feels good to have beaten Spain," Nagai said. "We have never beaten them before at any level. We look forward to now trying to get to the next stage (of the tournament)."

Japan now takes the lead in Group D after Honduras and Morocco played to a 2-2 draw.

All is not lost for Spain however, who are trying to add an Olympic gold along with its World Cup and Euro Championship, the Spanish lost the first game of the 2010 World Cup to the Swiss before winning the country's first ever World Cup.