Alison Riske-Amritraj suffered another early exit as the Pan Pacific Open began in Tokyo on Monday.

Riske-Amritraj reached the last 16 at the US Open earlier this month but has struggled in Asia since then.

She was the top seed at the Chennai Open last week, only to lose in straight sets in the first round to Anastasia Gasanova.

And the American fell at the first hurdle again in Japan.

Riske-Amritraj was drawn against compatriot Claire Liu, who was coming off back-to-back defeats to Anastasia Potapova and without a win since qualifying for the Canadian Open last month.

But Liu brushed aside the seventh seed 6-2 6-3 to set up a meeting with Elise Mertens in the second round.

Mertens eased through with a 6-0 6-3 win over Wang Qiang, while Petra Martic was similarly comfortable in a 6-1 6-1 defeat of Rina Saigo.

Saigo was one of two home hopefuls to depart on Monday as Qinwen Zheng won 19 points in a row en route to beating Misaki Doi 6-2 6-4.

At the Korean Open, Zhu Lin was the only seed in action and got the better of Jang Su-jeong in straight sets.