REFILE-Athletics-Olympic champion Liu breaks 50km world record - IAAF

March 9 (Reuters) - Rio Olympics race walk champion Liu Hong broke the 50km world record and became the first woman to dip under the four-hour mark at an event in Huangshan on Saturday, the International Association of Athletics Federations (IAAF) said.

Liu, who won the Olympic distance 20km gold in Rio, clocked three hours, 59 minutes and 15 seconds for the longer race, the IAAF said in a statement, clipping more than five minutes off the previous record (4:04:36) set by compatriot Liang Rui in Taicang last year.

The 31-year-old now holds the world record for both the 20km and 50km distances, having clocked 1:24:38 in La Coruna, Spain in 2015 for the shorter distance.

She also won the 20km gold at the 2011 and 2015 World Championships.

(Reporting by Greg Stutchbury; Editing by Peter Rutherford)