Skipper Babar Azam cracked a fighting century with great support from opener Abdullah Shafique Tuesday as Pakistan thwarted Australia's hopes of a quick win in the second Test in Karachi. 

Set a daunting 506-run target, Azam knocked his sixth Test century -- and second against Australia -- to guide Pakistan to 192-2 and raise hopes of an improbable victory, or even a fighting draw.

At the close Azam was unbeaten on 102 and Shafique 71 as the pair added 171 for the third wicket, leaving the home team needing another 314 runs in the 90 overs of the final day for a win, or bat out three sessions for the draw.

Pakistan lost Imam-ul-Haq (one) and Azhar Ali (six) before Shafique and Azam led the fightback, leaving Australia wicketless in the last session -- despite taking the second new ball after 80 overs.

Azam top-edged a sweep off spinner Mitchell Swepson towards short fine-leg for two to reach the three-figure mark, his first in 21 innings since his 143 against Bangladesh in Rawalpindi in February 2020.

Azam's hundred came in 247 minutes with 12 boundaries.

Shafique was as solid as his skipper, having so far hit four boundaries and a six as he and Azam batted defiantly for 265 minutes.

No team has ever chased more than the 418-7 that West Indies did against Australia at Antigua in 2003, while Pakistan's highest successful chase was 377 against Sri Lanka at Pallekele in 2015.

Australia, resuming their second innings at 81-1, batted for just 26 minutes at the start of play to add 16 runs before declaring on 97-2.

The visitors scored 556-9 declared in their first innings then dismissed Pakistan for 148.

The home team had hoped Azhar would anchor the second innings but the senior batsman was trapped lbw by Cameron Green when trying to evade a short-pitched delivery.

Azhar chose not to review as he trudged off but was left to regret it as television replays showed he had gloved the ball.

At 21-2, Australia seemed to have the upper edge and were looking to take a 1-0 lead in the three-match series but their efforts were thwarted by a slow turning pitch and the brilliance of Pakistan's batting pair. 

Australia could have had Shafique on 20 but the experienced Steve Smith spilled a straightforward catch in the slips off pacer Pat Cummins.

Despite cracks on the National Cricket Stadium pitch, Australian spinners Nathan Lyon and Swepson failed to get vicious turn. 

Earlier, Haq and Shafique were all caution as it took them until the fifth over to score the first run, before Lyon struck.

The in-form Haq, who scored a hundred in each innings of the drawn first Test in Rawalpindi, was trapped lbw for one as he failed to connect with a sliding delivery.

Earlier, Marnus Labuschagne was bowled off a sharp Shaheen Shah Afridi delivery for 44 to prompt skipper Cummins to call the innings to a close with first-innings century-maker Usman Khawaja, who was born in Pakistan, remaining 44 not out.

Australia are on their first tour of Pakistan since 1998, having previously refused to tour the country because of security fears.

Pakistan vs Australia second Test scoreboard

Australia 1st innings 556-9 dec (Usman Khawaja 160, A. Carey 93, S. Smith 72; Faheem Ashraf 2-55, Sajid Khan 2-167)

Pakistan 1st innings 148 (Babar Azam 36; M. Starc 3-29

Australia 2nd innings (overnight 81-1)

Usman Khawaja not out                  44

D. Warner c Alam b Hasan                7

M. Labuschagne b Shaheen               44

Extras (lb2)                            2

Total (for 2 wkts dec, 22.3 overs)     97

Fall of wickets: 1-20 (Warner), 2-97 (Labuschagne)

Did not bat: S. Smith,  T. Head,  C. Green,  A. Carey,  M. Starc,  P. Cummins,  M. Swepson,  N. Lyon 

Bowling: Shaheen 6.3-0-21-1, Hasan 7-0-23-1, Sajid 5-0-31-0, Ashraf 3-0-13-0, Nauman 1-0-7-0

Pakistan 2nd innings

Abdullah Shafique not out              71

Imam-ul-Haq lbw b Lyon                  1

Azhar Ali lbw b Green                   6

Babar Azam not out                    102

Extras: (b4, lb2, nb4, w2)             12

Total (for two wkts; 82 overs)        192

To bat: Fawad Alam, Mohammad Rizwan, Faheem Ashraf, Sajid Khan, Hasan Ali, Nauman Ali, Shaheen Shah Afridi

Fall of wickets: 1-2 (Haq), 2-21 (Azhar)

Bowling: Starc 12-5-29-0 (nb1), Cummins 13-5-35-0 (nb1), Swepson 27-6-57-0 (nb1, w2), Lyon 22-4-50-1, Green 8-2-15-1 (nb1)