Belgium's hopes of making the second phase remain in the balance after a disappointing draw with unfancied Tunisia.
Belgium opened the scoring after 13 minutes with a well-worked goal for Marc Wilmots but Tunisia hit back almost immediately, Raouf Bouzaiene scoring a stunning free-kick.
In stifling heat and 95% humidity in Oita's Big Eye stadium, Tunisia, so impressive in the first half, went into defensive mode for the second 45.
But though Belgium launched a series of attacks in an attempt to secure the winning goal, Tunisia's defence held firm to register their first point of the competition.
The result leaves Belgium needing a win against Russia in Friday's final Group H game to confirm their qualification for the second phase, while Tunisia must beat current group leaders Japan by more than two goals.
Tunisia, stung by a 2-0 defeat in their opening game against Russia, were much the brighter of the teams in the first half and it was somewhat against the run of play when Belgium opened the scoring after 13 minutes.
From a Peter van der Heyden cross, Derby County's Branco Strupar cushioned a perfectly weighted knock-down to Wilmots who pounced to score his 27th international goal.
But Tunisia refused to be bowed and if anything upped the tempo.
Just four minutes later, their creative industry was rewarded when Bouzaiene pulled them level.
The busy Slim Ben Achour was fouled just outside the box and Bouzaiene stepped up to curl a superb left-foot shot past goalkeeper Geert de Vlieger into the top corner.
Tunisia continued to make the more clear-cut chances, with lone striker Ziad Jaziri a constant menace to the Belgian defence, and they were unlucky not to take a first-half lead.
Jaziri's best chance came after 20 minutes when he wriggled his way into the box, only for his shot to go wide.
But Belgium's defence withstood the pressure and they had opportunities to restore their lead when, approaching the end of the first-half, Tunisia gave away two free-kicks in dangerous areas.
However, Strupar and Wilmots were unable to take advantage, both of their shots failing to clear the Tunisian wall.
In the second half, Belgium went desperately in search of a winner but as the minutes ticked by, their energy levels visibly dropped along with the quality of their build-up play.
Indeed, Tunisia could have sneaked an unlikely second goal in the dying moments when Kaies Ghodbane latched onto a cross just outside the area but his fierce shot was tipped over by De Vlieger.
And as the final whistle blew, it was the dogged Tunisians who celebrated, while Belgium rued their ageing side's inability to turn pressure into goals.
Tunisia: Boumnijel, Badra, Jaidi, Gabsi (Sellimi 67), Bouzaine, Ghodbane, Trabelsi, Bouazizi, Melki (Beya 88), Ben Achour, Jaziri (Zitouni 77).
Subs Not Used: Bejaoui, Clayton, Jaouachi, Jelassi, Marzouki, Mhadhebi, Mkacher, Mkademi, Thabet.
Booked: Gabsi, Ghodbane, Trabelsi, Melki.
Goal: Bouzaine 17.
Belgium: de Vlieger, Deflandre, De Boeck, Van Buyten, Van Der Heyden, Simons (Mpenza 74), Verheyen (Sonck 46), Wilmots, Vanderhaeghe, Goor, Strupar (Vermant 46).
Subs Not Used: Boffin, Englebert, Herpoel, Peeters, Thijs, Van Kerckhoven, Van Meir, Vandendriessche, Walem.
Booked: Van Buyten.
Goal: Wilmots 13.
Referee: M Shield (Australia).