Nairobi — Kenya's Rosemary Wanjiru surged to number six on the women's world marathon all-time list as she clinched victory at the Tokyo Marathon on Sunday morning.

Wanjiru ran 2:16:28 for the seventh-fastest women's marathon performance in history, winning by 28 seconds ahead of Ethiopia's Tsehay Gemechu who also dipped under 2:17, herself becoming just the eighth woman to ever achieve the feat.

Contesting the second marathon of her career after a 2:18:00 debut for the runner-up spot in Berlin last year, long-time Japan based Wanjiru was always among the leaders.

A seven-strong pack went through 5km in 16:19, Wanjiru running with last year's runner-up Ashete Bekere and her Ethiopian compatriots Tigist Abayechew, Worknesh Edesa and Gemechu, as well as Japan's Mizuki Matsuda, through 10km in in 32:34.

Japan's woman-only national record-holder Mao Ichiyama, who ran 2:20:29 in Nagoya in 2020, had explained at the pre-event press conference that she fractured a rib in December and she dropped back by 10km, running 23 seconds behind the leaders.

Matsuda was the next to lose touch but was still on Japanese record pace as the speed picked up again, a sub-16:00 5km split taking the leaders to 15km in 48:32.

The women's race was down to four by 20km, the tempo having eased slightly as Wanjiru, Edesa, Bekere and Gemechu reached that point in 1:04:44. Matsuda was just over a minute behind them, clocking 1:05:52.

The leading quartet remained together behind the two pacemakers through 25km in 1:21:07, but a few kilometres later that group of four, led by Wanjiru, decided to leave the pacers behind.

The tempo had slipped to 2:17 pace at 30km, reached in 1:37:25, but Wanjiru and Gemechu forged ahead over the next couple of kilometres.

Wanjiru was running solo by 39km but upped her pace to a projected 2:16:20 finish at the 40km mark, passed in 2:09:14, and she had a 19-second lead over Gemechu.

Wanjiru continued to glance over her shoulder during the closing kilometre but she had nothing to worry about and she crossed the finish line well clear, evidently elated with her victory and big 2:16:28 PB.

Gemechu also broke 2:17, finishing 28 seconds back in 2:16:56, while Bekere was third in 2:19:11 and Edesa fourth in 2:20.13.

The 2016 Olympic 10,000m fifth-place finisher Betsy Saina, racing her first marathon as a US citizen and as a mother, worked her way through the field to finish fifth in a PB of 2:21:40.