Bangladesh are three wickets away from a famous Test series win at home after spinner Taijul Islam took 4-113 to rattle Pakistan despite a rearguard by the opposition batters on Tuesday.
Pakistan ended day four on 316-7, needing another 121 runs for victory in what would be a record chase of 437 on the fifth and final day in Sylhet.
Mohammad Rizwan, on 75, and Sajid Khan, on eight, were unbeaten at the close of play.
Left-arm spinner Taijul struck key blows, including Babar Azam for 47 and Salman Agha on 71, to keep Bangladesh in the hunt for their first-ever Test series win over Pakistan at home.
Bangladesh, who won the opener of the two-match series, also closed in on back-to-back Test series victories over Pakistan -- having whitewashed them 2-0 on Pakistani soil in 2024.
Pakistan slumped to 162-5 and were heading towards a tame defeat before Rizwan and Agha put on 134 runs to raise hopes of Test cricket's highest chase.
West Indies currently hold the record for the 418 they scored to beat Australia in Antigua in 2003, while Pakistan have never successfully chased more than 377.
Pakistan lost their overnight openers early before captain Shan Masood and Azam steadied the ship with a counter-attacking partnership that guided them to 101-2 at lunch.
But the afternoon session shifted the momentum back in the hosts' favour. Bangladesh removed Azam after wicket-keeper Litton Das took a stunning catch behind the stumps off Taijul.
Nahid Rana then cleaned up Saud Shakeel with a wide yorker for just six, and Taijul snared Masood for a determined 71, with Mahmudul Hasan Joy taking a sharp catch at short leg.
Pakistan slipped to 200-5 at tea, but it was the stubborn sixth-wicket stand between Rizwan and Agha that frustrated Bangladesh.
But Taijul then deceived Agha with a well-disguised arm ball to rattle his stumps and Hasan Ali fell without scoring two overs later, caught by captain Najmul Hossain Shanto at first slip.
Rizwan and Sajid then batted out the remaining overs.
However, Bangladesh pace bowling coach Shaun Tait remained confident the side would get over the line on day five.
"I think we'll bowl them out. I hope," he said.
"Our guys stayed in the fight, stayed in the contest. They got on top of us for a period of time but to take those two wickets towards the end -- we went into the changing rooms fairly happy."
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Pakistan batting coach Asad Shafiq said: "I have a lot of hope because of the way we responded as a batting unit today. If this partnership between Rizwan and Sajid goes long, I am very optimistic."