Australia's bowlers shared the wickets, delaying Nathan Lyon's 500th as Pakistan bundled out for 271 in their first innings in the first Test at the Perth Cricket Stadium on Saturday.

The hosts took a 300-run lead on day three of the first test. Off-spinner Lyon remained on 499 test wickets after taking 3-66. Imam-ul-Haq top-scored with 62 for Pakistan, bowled out in 101.5 overs.

Australia chose not to enforce the follow-on, ending the day at 84-2 from 33 overs after posting 487 in their first innings.

"I think batting looked really tough there at the end. As the game goes along, I think the cracks will come more into play," said Australia paceman Josh Hazlewood, who took 1-49.

Resuming on 132-2, Pakistan almost lost Khurram Shahzad to a run-out on the first ball, but skipper Pat Cummins (2-35) prevented further damage, clean-bowling the nightwatchman (7) two deliveries later.

Imam, who uncharacteristically danced past a Lyon delivery to get stumped by Alex Carey, had consolidated with Babar Azam (21) but a collapse before lunch saw three quick wickets lost for 14 runs.

Some resistance from Agha Salman (28 not out) propped up Pakistan. Lyon got his second stumping for wicket 499 when Aamer Jamal (10) fell.

Part-time spinner Travis Head ended the Pakistan innings, drawing Shaheen Afridi into a slog-sweep, caught by Usman Khawaja at mid-on.

"Travis said that when they replay your 500th wicket, you don't want it to be a tail-ender; you want it to be a good wicket up the top," joked Hazlewood.

In the post-tea session, Australia lost first-inning centurion David Warner for a duck and Marnus Labuschagne for two as Shahzad's double-strike threatened to inject some spice into the contest.

Pacers Shahzad and Afridi, understanding the Perth Stadium conditions better in their second effort, restricted the hosts to seven runs in the first 10 overs, bowling with increased hostility.

Khawaja and Steve Smith steadied the ship, with a late scare when Smith hooked Afridi just over the head of a deep, fine leg for six. They ended the day unbeaten at 34 and 43, respectively.