T20 World Cup, Group 1, Lord's
Bangladesh 117-5 (20 overs): Mostary 42 (48); Mlaba 2-22
South Africa 118-6 (19.2 overs): Dercksen 45 (45); Nahida 2-24
South Africa won by four wickets
Earlier, South Africa stuttered but ultimately applied the pressure to India by beating Bangladesh by four wickets in their final group match.
Having beaten India and piled up 208-1 against Netherlands in their previous two games, they put in an indifferent batting performance reminiscent of their opening two games.
Captain Laura Wolvaardt fell to the first ball of the chase, her off stump knocked back by a Marufa Aktar inswinger, and when Dane van Niekerk was trapped lbw for three the Proteas were 59-3 at the halfway stage.
Annerie Dercksen threatened to take them home but she edged behind for 45 in the 15th over after which the boundaries dried up and the tension rose.
Marizanne Kapp was run out for 16 and Nadine de Klerk was caught at deep mid-wicket with five runs still needed before Chloe Tryon edged a four and cleared the off side to secure victory with four balls to spare.
South Africa were at least better with the ball.
Kapp bowled Juairiya Ferdous with the first ball of the match and, despite some middle-order resistance through a careful 42 by Sobhana Mostary and the late flurry of captain Nigar Sultana's 32 not out, Bangladesh still only made 117-5.
But, after an affair far more tense than it should have been, they progress as they look to end a run of three successive final defeats at World Cups.
On this evidence they must improve to beat England, however.