PARIS (Reuters) - Champion Serena Williams swatted aside the limp challenge of Elina Svitolina 6-1, 6-1 on Wednesday, to reach the quarter-finals of the French Open.

The world No. 1 rarely sparkled on a damp, dank centre court at Roland Garros, but always wielded enough firepower to see off the Ukrainian 18th seed in a match that was delayed by two days due to the fickle Parisian weather.

Empty green seats outnumbered raincoat-clad fans by around five to one on the Parisian showcourt, and the heavy, slow balls meant there was little artistry to entice greater numbers.

Although spluttering from time to time - Williams fired the odd serve alarmingly long; netted the occasional simple groundstroke - the top seed always did enough to neuter her scurrying opponent.

The American will play Carla Suarez Navarro or Yulia Putintzeva for a spot in the semis.