Brisbane: A helmet torn off, arms aloft, a kiss of the Australian crest and fist pounding chest. So was the emotional celebration of Steve Smith as he completed one of his finest test centuries in the series-opening Ashes test in Brisbane on Saturday.

With Australia wobbling at 76 for four on day two, Smith dragged his side back from the brink over eight-and-a-half hours of gut-busting graft and strode off the Gabba after tea on day three with an unbeaten 141 from 326 balls.

His 21st test ton and sixth against England helped nudge Australia in front of the tourists' 302 and inspired paceman Josh Hazlewood to grab two wickets late in the day.

With England 33 for two and holding a seven-run lead, the match is still very much within the tourists' hands.

But in grinding his way through the slowest of his test tons, Smith showed that he would carry his entire team to victory on his own back if forced to.

"It just meant a lot. Ashes series are always huge," the 28-year-old told reporters when asked about his stirring celebration.

"I want to lead from the front as much as I can with my performance and the way I bat.

"All of it came out when I got to 100. I had to very work hard, I think it was my slowest hundred. I had to work and be really disciplined and resilient.

"To get through those periods and get to a position where we are now, it's relatively pleasing."

It was a classic understatement from the no-fuss captain whose 17 runs in the morning session came with the speed of a well-fed sloth after he resumed on 64.

His batting partners crumbled around him and England captain Joe Root set defensive fields in a bid to suffocate his output.

On 97, he faced eight dot balls before Broad gave him an opening and he punched the fuller, wider delivery through the covers for four to complete one of his grittiest hundreds.

Tail-ender Pat Cummins gave him fine support with a knock of 42 from 120 balls but Smith, alone, seemed impervious to the wily plans of England's veteran pace duo, James Anderson and Stuart Broad.

In praising Smith, Broad also revealed his lower estimation of Australia's other batsmen, with only Shaun Marsh able to post a half-century in support of his captain.

"The less balls we can bowl at Steve Smith and the more we can bowl at the batsmen at the other end, the better for us," said Broad, who called on one of his own team mates to build a "Smith-like" innings on Sunday.

"He played brilliantly. That's what you come to expect from him in Australia.

"He played with a lot of patience, he was very disciplined around his off-stump, but also credit to our bowling attack.

"We didn't let them get away from us at any stage and we've seen as a batting group, if someone shows a lot of patience and gets stuck in, it can be quite hard to get them out."