World No 1 Serena Williams lashed out at "sexist" and "racist" comments from the head of Russian tennis on Sunday after he jokingly called her and her sister Venus the "Williams brothers".

Williams applauded swift action from the Women's Tennis Association, which fined Russian federation chief Shamil Tarpischev $25,000 and banned him from tennis for a year.

"Well I think the WTA did a really great job in taking the initiative and immediately taking actions," Williams said ahead of the WTA Finals in Singapore.