Pakistan declared their first innings at 476-4 on Saturday in the first Test against Australia after brilliant hundreds from Azhar Ali and Imamul Haq on the second day in Rawalpindi.

Ali scored 185 and Haq 157 as Australia toiled hard after Pakistan won the toss and batted on a flat, batting-friendly Rawalpindi Cricket Stadium pitch.

The 37-year-old lofted spinner Nathan Lyon for his eighth boundary towards mid-wicket to complete his 19th hundred in his 92nd Test.

With that, Pakistan reached 312 without losing another wicket after starting the day on 245 for one.

He has been Pakistan's mainstay in the Test batting line-up since making his debut in 2010, and boasts a triple hundred against the West Indies — the first since day-night Tests were introduced.

Haq was the slowest of the Pakistan pair on Saturday morning, adding just six runs in the first hour and not hitting a boundary until the 90th minute.

Haq was lucky to survive a caught-behind appeal on 143 off Lyon the Australians didn't challenge when replays showed it hit the bat.

Meanwhile, Skipper Babar Azam made 36 while Mohammad Rizwan (29) and Iftikhar Ahmed (13) remained not out.

For Australia, Pat Cummins, Lyon and Marnus Labuchagne took a wicket apiece while Azam was run out.

Earlier today, the Australian and Pakistan teams paid tribute to legendary spinner Shane Warne with a minute's silence as play resumed.

“It's a sad way to start the day,” the television commentator said as players wore black armbands to pay homage to Warne, who died of a heart attack in Thailand on Friday.

The handful of early-morning spectators in the stands also stood in respect.

The Australians were playing in Pakistan for the first time since 1998, having declined to tour previously because of security issues.

Warne was widely regarded as one of the greatest cricketers of all time — a larger-than-life character whose tally of 708 Test wickets has been surpassed only by fellow spinner Muttiah Muralitharan.

His death is a double blow for Australia after another cricketing great, Rod Marsh, also died on Friday after suffering a heart attack.

Cummins admitted the team was shaken.

“Yeah, these are really tough times with, you know, both Rod and Shane gone,” the Australian skipper told the host broadcaster ahead of the day's play.

“I just encourage everyone to talk about it.”

Cummins said Warne was popular around the world.

“You know, his showmanship and all those things that he brought to Australian cricket are probably my longer-lasting memories.

“I think playing across the world, you realise just it wasn't only Aussies that felt that it was ... in all corners.”