HONG KONG, May 29 (Reuters) - Chinese internet giant Tencent Holdings' mobile game "Dungeon and Fighter" was the top-selling app on Apple's App Store in China this week, surpassing the company's existing flagship games after it spent years looking for a new marquee title.

The side-scrolling action game, developed by South Korea's Nexon and published by Tencent, became the top-selling app in China hours after it was launched on May 21 and it has stayed there since, according to app tracking platform Appmagic.

Tencent's "Honor of Kings" and "Peacekeeper Elites" have long been China's most popular games but they have recently shown signs of declining revenue as their popularity ebbed.

Globally, "Dungeon and Fighter" mobile ranked as the world's second top-selling app last week, only behind short video platform TikTok and ahead of Honor of Kings and YouTube, which came in third and fourth, according to Appmagic.

The video game is estimated to have earned more than $40 million in revenue on Apple devices after receiving over 2.4 million downloads, according to Appmagic.

Robin Zhu, senior analyst at Bernstein, said that Appmagic's number aligns with data recorded by another app tracking firm called Sensor Tower.

But he said that the game actually makes more money because the $40 million figure was only Tencent's and Nexon's cut, excluding Apple's share of the revenue.

"Gross billings-wise, the Sensor Tower data suggests you're looking at 1.2 to 1.5 billion yuan ($206.95 million) of receipts since launch," he said. Gross billing refers to the gross amount that users have spent on the game.

He said that "Dungeon and Fighter" mobile's strong performance is on track to meet Nexon's expectation of 3 billion yuan in gross billings during the game's first month of launch.

Officially named "Dungeon and Fighter: Origin", the game is a mobile adaptation of the "Dungeon and Fighter" computer game, one of the world's most profitable computer games which Tencent also publishes.

The game, under development for seven years, was released in South Korea in 2022 and became an instant hit. But its China release was delayed after the government cracked down on the gaming industry between 2018 and 2022. ($1 = 7.2483 Chinese yuan) (Reporting by Josh Ye; Editing by Jacqueline Wong)