Heather Watson is out of the Korea Open following a straight-sets defeat by Ukraine's Marta Kostyuk in Seoul.

The 32-year-old qualifier, ranked 183rd in the world, lost 6-2 6-2 in the second round.

World number 18 Kostyuk, 22, will meet Russian Diana Shnaider, 20, in the quarter-finals after sealing a straightforward victory.

British number two Emma Raducanu earned a hard-fought win against American Peyton Stearns on Tuesday and will play China's Yue Yuan for a place in the last eight.

Watson, who last month failed to qualify for the US open main draw, responded immediately after losing serve in her opening game - but Kostyuk won five of the next six games to take the opening set.

The Briton, whose opening victory over China's Jia-Jing Lu was only her third main draw win this season, could not mount a fightback as Kostyuk raced to victory with a double break in the second set.