Azhar Ali hit a stunning triple hundred on his 50th Test appearance as Pakistan continued to dominate West Indies on day two of the first five-day clash in Dubai.

Opener Azhar lit up day one of the day-night Test - the second in history - by making it to stumps unbeaten on 146, but showed tremendous staying power as he reached 302 in 469 deliveries, spending 11 hours at the crease in total.

The superb knock helped Pakistan register a first-innings total of 579-3, with captain Misbah-ul-Haq - partnering Azhar at the time - opting to declare as soon as the 31-year-old had clocked up the milestone.

Azhar becomes the 29th man to score a triple ton and brought up his 4,000th Test run in the process.

Leon Johnson was an early victim of Yasir Shah as the tourists finished the day 69-1, trailing by 510 runs.

Azhar has made light of any concerns regarding use of the pink ball over the last two days and set about building on his impressive first-day showing early on Friday.

The Windies had chances to halt Azhar - most notably when Jermaine Blackwood dropped him at lone slip with the batsman on 190.

Asad Shafiq (67) fell to Devandra Bishoo (2-125) in the 109th over, but Babar Azam proved another capable accomplice on his Test debut.

Having posted three centuries in the recent one-day series, Azam (69) helped Pakistan complete 100-run stands for the first three wickets for only the third time.

Pakistan's 400th Test was fittingly marked by the team surpassing 400 runs shortly after Azhar had reached 200, but the hosts' star man was not done there.

Azhar got to 250 in bizarre fashion - Johnson collected the ball before throwing back to an unsuspecting Miguel Cummins on boundary, with the ball reaching the fence as a result.

The Windies were consequently penalised for an overthrow in an incident that summed up their dismal showing.

Azam eventually fell to Bishoo, bringing Misbah to the crease, and the skipper was happy to play a supporting role in seeing Azhar past the 300 mark, before swiftly calling an end to the innings.