Yuya Osako ensured four-time champions Japan began their 2019 Asian Cup campaign with a 3-2 victory over Turkmenistan as he inspired a second-half fightback on Wednesday.

Samurai Blue coach Hajime Moriyasu promised before kick-off that his side were in "top shape", but they were outplayed by Turkmenistan for 45 minutes and the minnows were dreaming of a first finals win when captain Arslanmurat Amanov thundered in the opener.

However, Osako scored twice after half-time before Ritsu Doan added a third and a crisis was averted for Japan and Moriyasu, who had also outlined the need to win by any means after seeing fellow big-hitters Australia slip up against Jordan.

Ahmet Atayev's penalty made things interesting once more, but Japan can breathe a little easier ahead of their second match against Oman as they look to secure swift passage through to the next stage.

Doan and Mekan Saparov wasted early close-range headers at either end, before Shuichi Gonda was caught off guard by Amanov's sublime opener that fizzed high past the wrong-footed goalkeeper from 30 yards.

Gonda was soon in the spotlight again as he parried behind to deny Ruslan Mingazov, but Japan emerged for the second half with renewed vigour and Osako turned the game on its head.

The forward turned smartly in the area to arrow a low shot into the net for the equaliser and then tapped in a second when Yuto Nagatomo beat Saparov at the byline.

Doan worked space on the left side of the area and picked his spot to seemingly put the result beyond doubt, although the erratic Gonda set nerves jangling again in the closing stages as he brought down Altymyrat Annadurdyyev and could not then keep out Atayev's spot-kick.

However, Japan held on to make a winning start.