Mitchell Marsh joked he was glad to go from "negative 50" to an unbeaten 177 in a crushing eight-wicket win over Bangladesh that set Australia up for Thursday's World Cup semi-final against South Africa in Kolkata.

Saturday's victory meant Australia ended the group stage with a seventh successive win after two defeats at the start of their quest for a record-extending sixth World Cup title.

They were already assured of a last-four clash with the Proteas -- a repeat of the dramatic 1999 tied semi-final between the countries that allowed Australia to reach that year's final -- before a ball was bowled in Pune.

But they will go into the knockout game buoyed by chasing down a target of 307 against strugglers Bangladesh with 32 balls to spare.

Marsh's second hundred of the tournament, following 121 against Pakistan, was also his highest score but only third century in 87 one-day internationals.

He also shared century partnerships with David Warner 53 and Steve Smith, the star batsman 63 not out after returning from vertigo.

"It's always a great honour to score a hundred, but I was pretty cooked to be honest," said Marsh, now batting at number three.

"I was just starting to cramp at that stage, so I was trying to keep my heart rate low and not exert too much energy," the 32-year-old added following a 132-ball innings including 17 fours and nine sixes."

The paceman said he felt he owed Australia runs after conceding an expensive 48 in four wicketless overs during Bangladesh's 306-8 -- their highest total of the tournament.

"I started at negative 50 after my bowling, so I had to get a few (runs) back.

"With the amount of improvement with all cricket teams around the world, there's been not one easy game so to get to the semi-finals is great. But we're very excited about what lies ahead."

 'Chase whatever is in front of us' 

Australia, however, have conceded several totals of over 300 during the 10-team round-robin phase of the World Cup, notably during a 134-run defeat by South Africa and, despite scoring 388 themselves, in a thrilling five-run win over New Zealand.

Afghanistan's 291-5 almost proved too much for Australia in Mumbai on Tuesday before Glenn Maxwell's stunning unbeaten 201 secured a three-wicket triumph after a collapse to 91-7.

But Marsh said there were explanations for Australia's relative lack of wickets with the new ball.

"There's probably a number of things that that comes down to. There's been some really 'fat' (batsmen-friendly) wickets and some small grounds," he said.

"I didn't realise how small this one was, even though I played here a little bit. There's a lot of good teams out there, a lot of teams have chased down big totals.

"So I think it's about having a mentality to keep taking wickets, but understanding that when guys get on top that that's going to happen at this level and whatever is put in front of us, we try and chase it down."