Smith completed his 14th Test ton and passed 5,000 Test runs

South Africa openers Graeme Smith and Neil McKenzie put on a unbeaten 405 on day one of the second Test against Bangladesh in Chittagong.

Smith (223) and McKenzie (169) need nine runs to beat the world record opening partnership in Test cricket.

Choosing to bat first, the pair raced to 92 by lunch and continued to punish Bangladesh bowling attack thereafter.

Smith's fourth double ton is a South African record, while McKenzie's century was his first in seven years.

And on a pitch seemingly custom-made for the batting team, Smith and McKenzie look well poised to surpass the 413 set by India's Pankaj Roy and Vinoo Mankad against New Zealand in Chennai in 1956.

"There are a lot of boys in there happy we won the toss," said Smith.

On a day of records, Smith passed 5,000 Test runs and broke his own record for the biggest opening stand in South African history, which he had set with Herschelle Gibbs against Pakistan in 2003.

606: DEBATE Your thoughts on Smith, McKenzie and the action in Chittagong

McKenzie scored his first century for seven years and looks likely to participate in South Africa's biggest partnership for any wicket.

That mantle is currently held by Jacques Rudolph and Boeta Dippenaar, who put on an unbeaten 429 for the third wicket against Bangladesh in 2003.

Smith, leading the Proteas for a record 54th time, completed his 14th Test century by cutting Shakib Al Hasan through point.

McKenzie reached his third Test hundred when he smashed Mohammad Rafique for six over long-off.

Rafique dropped McKenzie, on 131, off his own bowling but otherwise the 32-year-old provided Smith with faultless and emphatic support.

McKenzie (left) and Smith look happy with their day's work

Bangladesh, whose captain Mohammad Ashraful used seven bowlers, looked lost for ideas and Smith brought up his double ton by working Mashrafe Mortaza through midwicket for four.

"I have got quite a few double hundreds now, so I know how tough it is to get there," said Smith. "You have to concentrate really hard all the way through

Slow left-armer Shakib Al Hasan was the only bowler to emerge with any credit, his 10 overs going for just 33.

"The wicket played really well. Once you get in, it is all about making every run count."

Bangladesh paceman Shahadat Hossain was all praise for the way the South African openers exploited the conditions.

"There was nothing in the wicket for the bowlers. They batted brilliantly throughout the day and did not give us any chances.