The Blue Samurai were headed for an ignominious draw in Saitama when Yamaguchi smashed a loose ball from a corner through a forest of legs and into the Iraqi goal.

The result gave Japan their second win in three final-round qualifiers and boosted under-fire coach Vahid Halilhodzic, who has endured calls for his resignation and has suffered reported player unrest.

It also lifts Japan's hopes of reaching a sixth straight World Cup at Russia 2018 as they draw temporarily level on points with Group B pace-setters Australia and Saudi Arabia, who face each other later.

As Borussia Dortmund forward Shinji Kagawa watched from the bench, Japan dominated the early possession but rarely threatened, with Hiroshi Kiyotake's 11th-minute piledriver their closest sight of goal.

But Genki Haraguchi put the hosts ahead with a brilliant piece of skill as he flicked Kiyotake's cross through his legs and beneath the diving body of goalkeeper Mohammed Hameed on 26 minutes.

AC Milan's Keisuke Honda should have made it 2-0 a minute later but he hit his close-range half-volley straight at the busy Hameed.

Iraq nearly equalised in first-half injury-time but Alaa Abdul-Zahra's volley, from a sweeping ball that dropped over his head, bounced kindly for Japan 'keeper Shusaku Nishikawa.

However, Iraq rocked the four-time Asian champions on 60 minutes when Saad Luaibi nodded Ahmed Yaseen's free kick just inside the post and past the diving Nishikawa.

Not content with a draw, Iraq poured forward in search of a shock victory, but it was Honda who very nearly grabbed the clincher when his header came off the post in the 80th minute.

And as six minutes of injury-time ticked away, Hiyotake's cross rebounded to 67th-minute substitute Yamaguchi, who buried the winner to send the stadium into ecstasy.

The top two sides from two groups of six book their ticket to Russia, while the two third-placed teams go into a play-off series.