Babar Azam leads Pakistan's fightback in Karachi Test against Australia

Babar Azam defied Australia's bowlers with a sparkling knock of 102 not out as Pakistan fought back on the fourth day of the second Test in Karachi on Tuesday.

Set a near-impossible target of 508, Pakistan seemed to be staring down the barrel at 21-2 in the 23rd over as the runs dried up.

However, captain Azam and opener Abdullah Shafique (71 not out from 226 balls) launched a superb counter-attack as the two added 171 from almost 60 overs and remained unbeaten at stumps to revive the hosts' hopes in a match that seemed lost when they were bowled out for 148 on the third day.

The scoring rate barely crept over two an over but the home batsmen showed tremendous application to keep Australia's quicks at bay, especially once the ball started to reverse early.

Azam endured a few nervous moments as he approached his ton in the final session. He inside edged Pat Cummins past his stumps to reach 99 and then top edged spinner Mitchell Swepson over fine leg to reach three figures. He finished the day on 102 from 198 balls.

The crowd cheers, the lion roars. @babarazam258 owns the day. #BoysReadyHain l #PAKvAUS pic.twitter.com/ndM0RNWPTG

Pakistan looked a long way from safety when opener Imam-ul-Haq was out lbw to Nathan Lyon and senior batsman Azhar Ali fell in a comical way, out 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.

Australia could have had Shafique on 20 but the experienced Steve Smith spilt a straightforward catch in the slip off pacer Cummins, a chance that could prove very costly for the visitors.

Earlier, Australia resumed their second innings at 81-1 and batted for just 26