Goalkeeper Pepe Reina saved a penalty but Liverpool slipped off the top of the Premier League after they were held to a draw at Portsmouth.
Kanu saw his penalty saved by Liverpool keeper Pepe Reina
Reina dived low to his right to save Kanu's penalty, after Alvaro Arbeloa had tugged the Nigerian's shirt.
Portsmouth were impressive and John Utaka should have at least hit the target from 14 yards.
Andriy Voronin grazed the Pompey crossbar, while David James saved from Yossi Benayoun and Peter Crouch.
Reds boss Rafa Benitez cut a frustrated figure on the touchline but Pompey, who have now played all of the so-called 'top four' in their opening six Premier League games of the season, were good value for their point.
And having left Fernando Torres, Ryan Babel and Steven Gerrard on the bench - no doubt mindful of the midweek Champions League tie with Porto - Benitez clearly took a gamble that did not pay off as his team failed to score for the first time this season.
Liverpool might have started without several of their star players but there was no doubting the skill and appetite with which they initially went about their work.
Benayoun, making his first Premier League start since his transfer to Anfield, and Crouch both enjoyed early strikes at goal.
Andriy Voronin, particularly lively operating along the front line, found himself in space with the opportunity to play a completely unmarked Jermaine Pennant through on goal but the Ukraine international got too much purchase on his pass.
Pompey - despite the return of Sol Campbell and the considerable presence of Papa Bouba Diop, who was making his debut in midfield - struggled to find any kind of rhythm in the opening stages.
However, Harry Redknapp's increasingly durable side eventually started to threaten, with two long balls causing chaos in the Liverpool area, while a shot from Benjani took a slight deflection and required a decent save from Reina.
And Pompey should have taken the lead after winning a penalty.
Arbeloa certainly had hold of the back of Kanu's shirt, although the infringement was completely needless and it took an excellent save from his compatriot Reina to atone of his error of judgement.
Pompey started to take control in midfield, with a Sean Davis strike forcing Reina into action again and by the break Liverpool's forward duo of Crouch and Voronin had become starved of service and increasingly ineffective.
Pompey striker Utaka wasted another brilliant opportunity to take the lead after the break, drilling his shot wide after the ball dropped to him 14 yards from goal.
Liverpool threatened next, Voronin looping a shot against the top of the crossbar from 18 yards after a slick move involving Pennant, Sissoko and Babel.
But it was a fragmented performance by the team who started the day top of the league, especially given that their last performance had led to them demolishing Derby 6-0 at Anfield.
Benitez had clearly seen enough and first introduced Torres, then Gerrard and eventually Crouch.
Torres and Gerrard almost combined to open the scoring but the Spaniard drilled his shot way over the crossbar after the England midfielder had ended a driving run forward by playing a superbly weighted pass.
Pompey, however, continued to threaten, with Diop heading wide and Muntari failing to make the most of a neat lay-off from Kanu, the Ghanaian's shot missing the target after taking a slight deflection.
Voronin was inches away from converting a low cross late on but Portsmouth were not to be denied their first clean sheet in the Premier League this season.
Portsmouth manager Harry Redknapp:
"He covered every blade of grass.
"I have always been a fan of his. He is big and he has a presence about him. He will do well for us.
"It was an even game and we had a couple of great chances.
"When you get the chance you have to stick it away against Liverpool and if we had got in front I'm sure we would have gone and won the game."
Liverpool manager Rafa Benitez:
"I think it is disappointing.
"But I think we played well, creating chances and good on the counter attack. I am really pleased with the players.
"I think we controlled the game in the first half but in the last 15 minutes it was very open."
Portsmouth: James, Johnson, Campbell, Distin, Hreidarsson, Utaka, Davis, Diop, Muntari, Mwaruwari (Kranjcar 67), Kanu.
Subs Not Used: Ashdown, Nugent, Taylor, Pamarot.
Booked: Diop, Johnson, Davis.
Liverpool: Reina, Finnan, Carragher, Agger, Arbeloa, Pennant (Gerrard 67), Sissoko, Alonso (Babel 77), Benayoun, Voronin, Crouch (Torres 62).
Subs Not Used: Itandje, Hyypia.
Booked: Alonso, Sissoko.
Ref: Mike Riley (Yorkshire).