Kenyan marathon runner Mary Keitany has announced her retirement at the age of 39 because of a back injury.

Keitany holds the world record for a women-only marathon with a time of two hours 17 minutes one second, which she set when winning her third London Marathon in 2017.

She also won the New York Marathon on four occasions.

"Now is the time to say goodbye - if only as an elite runner - to the sport I love so much," she said.

"After my successful 2019, when I had some good results including second place in New York, I was hopeful that I could still be very competitive internationally for several more years even though I am in my late 30s," Keitany added in her statement.

"However, I'm sad to say, a back injury that I suffered in late 2019 made a decision about my retirement for me.

"I couldn't get the treatment I wanted in Europe because of the pandemic-related travel restrictions last year and every time I thought I had got over the injury and started training hard, it became a problem again.

"As for the future, I haven't fully decided on my plans but I'm looking forward to spending more time with my family - my children are currently 13 and eight. In addition, I am involved with some local charitable enterprises."

Keitany's first global success came in 2007 when she won an individual silver and team gold at the World Half Marathon Championships.

A year after the birth of her first child in 2008, she claimed the world half marathon title in Birmingham, England. Her efforts also helped Kenya win the team title once again.

In 2010, she moved up to marathons and finished third in the New York on what was her debut and then a year later she won the first of her London Marathon titles.

Her second child arrived in 2013 and she once again made an impressive return to competition as she won three consecutive times in New York between 2014 and 2016 before winning or a fourth time in 2018.

She also set a world record at the 2011 RAK Half Marathon in the United Arab Emirates, a mark which stood for three years until it was broken by her compatriot Florence Kiplagat at a race in Barcelona.

One disappointment during her illustrious career was a fourth place in the London 2012 Olympic Games marathon.