The Japanese men's and women's teams never relinquished their first-leg leads as they breezed to a double victory Thursday in the Chiba international ekiden road relay.

The Japanese men covered the five-leg, 42.195-km course in one hour, 59 minutes and 47 seconds, while the country's six women combined to clock 2:15:30 over the same distance for a convincing victory even without Olympic marathon champion Naoko Takahashi.

First-leg runner Koichiro Nagata and anchor Kenichi Takahashi produced the fastest times in their legs to lead Japan to its fourth victory in the men's race. South Africa took second in 2:01:28 and Australia third in 2:03:07.

In the women's race, Ikumi Nagayama gave Japan an 8-second advantage after the opening 10-km leg before Mari Ozaki, Haruko Okamoto, Mami Kusunoki, Kayoko Fukushi and Megumi Tanaka successfully maintained the lead en route to the host's ninth straight victory.

All but Kusunoki turned in the best times for their legs of the race as Japan prevailed over runner-up Ethiopia (2:17:30) and third-place Kenya (2:18:18).

Takahashi, who set an Olympic record in winning the gold in Sydney in September, was with the Japanese team Thursday following her last-minute withdrawal from the race due to a knee injury.

"I've got pains in my right knee, which is familiar to me early in the marathon season," she said. "I particularly feel pains when I run downhill sections, and I decided to pull out of this race for fear of hurting the team's performance today," Takahashi concluded.