Japan have pulled off a huge shock in their opening Olympic fixture by beating tournament favourites Spain 1-0.

The match appeared to be following a familiar pattern early on as Spain took control of possession, but their final ball was lacking and Japan were looking increasingly threatening on the counter attack.

The underdogs took the lead after 35 minutes when Takahiro Ohgihara whipped in a corner that Yuki Otsu converted from close range, a lead that was almost doubled minutes later as Hiroshi Kiyotake rounded David de Gea only to put his shot narrowly wide.

Spain's nightmare first half was compounded on the stroke of half-time as Inigo Martinez was shown a red card for a last-man tackle on Kensuke Nagai.

Japan continued to impress in the second half, and almost extended their lead when Heigo Kigashi curled an effort towards the top corner, forcing a good save from De Gea.

Spain continued to struggle with the attacking pace of Japan, and could consider themselves lucky to still be just 1-0 down when Nagai and Kiyotake missed two chances in as many minutes, firing just wide on both occasions.

Spain began to take control of the match towards the latter stages, and almost got an equaliser when Juan Mata shot from inside the box, but Shuichi Gonda was equal to it.

Still, though, Japan refused to sit back and defend, and almost killed the game off with five minutes left as Nagai once again advanced on goal, but was denied by De Gea.

Hotaru Yamaguchi came close in injury time for the hugely impressive Japan, but could only fire his shot over as his side completed a massive upset to move top of Group D.

Next up for Spain will be Honduras, who drew 2-2 with Japan's next opponents Morocco earlier today.