Joe Root went past Alastair Cook as England's highest Test run scorer with an unconquered hundred against Pakistan, anchoring his team to 492-3 in the first Test in Multan on Wednesday.

The 33-year-old overhauled Cook's aggregate of 12,472 runs and became the fifth-highest scorer of all time after he drove seamer Aamer Jamal for a straight boundary to reach 71 just before lunch.

Root was still batting on 176 at the close on day three with his partner Harry Brook on 141 not out, taking England within 64 runs of Pakistan's first innings total of 556.

The pair added 243 runs for the unbroken fourth wicket, rebuffing Pakistan's bowling attack on a lifeless pitch that had punished England's bowlers on the first two days.

Root's memorable 481-minute knock includes 12 boundaries. Brook amassed the same number and added a six despite suffering cramps.

Root reverse swept spinner Abrar Ahmed for a single to reach his 35th Test hundred -- the sixth most by any batsman -- getting to the mark off 167 balls.

Brook reached his sixth hundred with a single off part-timer Saud Shakeel from 118 balls, adding to his previous three in England's 3-0 series rout of Pakistan two years ago.

Root added 136 for the third wicket with Ben Duckett, who made a robust 84 and showed no effect from a thumb dislocation on Tuesday that forced him to bat at number four.

Duckett was the only man dismissed in the second session, trapped leg-before by Jamal after hitting 11 boundaries.

All three Pakistan fast bowlers -- Shaheen Shah Afridi, Naseem Shah and Jamal -- have taken a wicket each. Frontline spinner Abrar has conceded 174 runs in 35 wicketless overs.

Pakistan also reviewed three not out decisions to no avail.

It was a day to remember for Root, who took 268 innings and 147 Tests to go past his former captain Cook's total of 12,472 runs from 161 Tests in a glorious career that ended in 2018.

Root also added 109 for the second wicket with Zak Crawley, who hit 13 fours in an 85-ball knock of 78.

Crawley failed to keep a flick down off Shaheen in the fourth over and was caught at the second attempt by Jamal at mid-wicket.

Duckett started with trademark aggression, taking five boundaries off Abrar and completing his 10th Test half-century off just 45 balls.

That helped Root accumulate steadily at the other end as he brought up his 65th Test fifty off 76 balls. He was applauded by a handful of England fans and teammates in the dressing room when he broke Cook's record.

The all-time list is headed by India's Sachin Tendulkar with 15,921 runs from 200 matches.

Cook said of Root during BBC radio commentary that he could "see him overhauling Sachin Tendulkar's record".

"I don't see that happening for Root to lose that hunger and ability to keep driving himself forward for the next couple of years," the former England opening batsman said.