The 20-year-old said "people should be embarrassed" after their reaction to her handshake snub of the world number two, who is competing as a neutral due to sanctions enforced in response to the war in Ukraine.

"I want to see people react to it in 10 years when the war is over," said world number 39 Kostyuk.

"I think they will not feel really nice about what they did."

Sabalenka took a routine 6-3, 6-2 win and stated that Kostyuk "didn't deserve to leave the court that way".

The 25-year-old Sabalenka, whose best result at Roland Garros is a third-round finish, was startled by the reaction from the crowd.

"It was a very tough match, tough emotionally," she said in her on-court interview.

"I thought the boos were against me so I felt a bit surprised.

"But then I felt your support."

Elsewhere on what was the first day of the main draw in Paris, Greece's Maria Sakkari became the first top-10 seed to be eliminated.

She fell 7-6, 7-5 to unseeded Czech Karolína Muchová in a hard-fought encounter lasting more than two hours.

It is the second straight year that eighth seed Sakkari, a previous Roland Garros semi-finalist, has been knocked out of the Grand Slam by Muchová.

"It's a little bit of déjà vu," said world number 43 Muchová.

"It was a very tough match, she is a very good player.

"I'm glad we didn't play a [second] tie-break, I managed the nerves." 

Third seed Jessica Pegula progressed to the second round following her 6-4, 6-2 defeat of American compatriot Danielle Collins.

She has yet to go beyond the quarter-finals of a Grand Slam singles event and is due to face Italian Camila Giorgi in the next round after she beat home favourite Alize Cornet.

The only upset in the men's singles came courtesy of Australian Thanasi Kokkinakis who blitzed British 20^th seed Dan Evans 6-4, 6-4, 6-4.