World number 89 Diyas had lost her only other meeting against the veteran American in 2015, but reversed that result with a 6-2, 7-6 (12-10) victory.

Diyas said it was a "special" moment to beat 40-year-old Williams, who captured her Miami titles in 1998, 1999 and 2001.

"I’m very happy with the win today, it was very tough," said Diyas.

"I looked up to Venus when I was little, she’s such a legend.

"I’m really happy how I handled the tiebreak.

"There were a lot of nerves, but happy I did it."

Americans Robin Montgomery and Katrina Scott, who were not even born when Williams last won the women’s singles crown in Miami, made their main-draw debuts at the Women's Tennis Association (WTA) 1000 event.

But the two 16-year-olds were both knocked out, with Montgomery losing 6-1, 3-6, 6-0 to Poland’s Magda Linette and Scott falling to a 6-2, 6-2 defeat to Romania’s Sorana Cîrstea.

Shelby Rogers came out on top against Madison Brengle in an all-American clash, triumphing 6-3, 6-3.

Australia’s Ajla Tomljanović secured a second-round meeting with Japan’s world number two Naomi Osaka following a 7-5, 6-0 victory over Russian Anastasia Potapova.

Barbora Krejčíková of the Czech Republic will face Poland’s French Open champion Iga Świątek in the next round after overcoming Russian Anna Blinkova.

Germany’s Laura Siegemund defeated American Christina McHale 6-3, 7-5, Sweden's Rebecca Peterson claimed a 6-2, 6-2 win over China's Wang Xiyu and Arantxa Rus of The Netherlands triumphed 6-3, 6-2 against Czech Marie Bouzková.

Estonian Kaia Kanepi saw off American Lauren Davis, 6-3, 7-5, while Argentina’s Nadia Podoroska thumped Egypt’s Mayar Sherif 6-3, 6-1.

Action is due to continue tomorrow with more women’s first-round matches and the start of the men’s singles.