BOSTON -- Stephen Sambu of Kenya won the B.A.A. 10K for the second straight year Sunday, edging countryman and 2011 Boston Marathon winner Geoffrey Mutai.
In the women's race, Ethiopia's Mamitu Daska also won for the second consecutive year. She was timed in a course-record 31:04, with Kenya's Betsy Saina six seconds behind.
On a sunny morning with temperatures in the low 60s, Sambu pulled away near the 5-mile mark and finished 10 seconds ahead of Mutai. Sambu set a personal best of 27 minutes, 25 seconds, beating his mark by 14 seconds.
"I am so happy," said Sambu, who turns 26 on July 7. "It makes me feel like I'm improving."
He and Mutai, running side by side, set a world record for 8 kilometers -- 22:01. Sambu did not know until after the race that the mark had fallen.
"Our plan from the beginning was to make the pace high," he said.
With many of nearly 8,000 runners heading onto the course in the opposite direction -- separated by a grass-covered median on Commonwealth Avenue -- Sambu made his break just after 8K.
"I was feeling good the whole way," he said. "I just increased the pace a little bit. I was thinking after 8K I knew I still had 2K to go. I was just thinking about finishing. I was feeling tired."
Mutai also won the 2011 New York City Marathon.
"The race was tough for me," he said. "It's good to be back in Boston. It was a good performance for me. I still have to get in shape."
In the women's race, Daska surpassed her personal best by 37 seconds.
"I didn't expect to run such a fast race today," she said through a translator.
The race started at Boston Common, headed up Commonwealth and turned around on the same street at Boston University. The course continued through Kenmore Square, a short distance from Fenway Park, before concluding at the Common. It was filled with twists and turns through the city's Back Bay section, making an early left near local landmark Cheers, the bar of television fame.
The 10K is part of the B.A.A. three-race medley. The 5K was in April, with a half marathon scheduled for October.