Serena Williams says comments by the head of the Russian Tennis Federation referring to her and older sister Venus as “brothers” were bullying, sexist and racist.

Shamil Tarpischev was fined $US25,000 ($A27,000) and suspended from tour involvement for a year for making the comments on Russian television. He also said the sisters were “scary” to look at.

Speaking Sunday ahead of her WTA finals defence in Singapore, Williams said Tarpischev’s comments were “very insensitive, sexist and racist and in a way bullying.”

She praised the WTA’s response to the remarks.

Tarpischev said Saturday he was unrepentant and that the comments were only meant as a joke.