Tokyo, July 24 : Men's world No. 1 Novak Djokovic of Serbia and women's world No. 8 Iga Swiatek of Poland won their opening-round matches in the Olympics tennis event at the Ariake Tennis Park here on Saturday. Daniil Medvedev, representing the Russian Olympic Committee (ROC) team since Russia is banned, also won his first-round match against Alexander Bublik of Kazakhstan 6-4, 7-6(8). Medvedev will now face India's Sumit Nagal in the second round. Nagal had beaten Denis Istomin of Uzbekistan 6-4, 6-7(6), 6-4. Among other winners in men's section were Italian Lorenzo Sonego, who beat Taro Daniel 4-6, 7-6(6), 7-6(3), ROC's Aslan Karatsev who trumped 6-3, 6-2 and Italian Fabio Fognini who beat Yuichi Sugita 6-4, 6-3. Besides Iga in the women's section, Czech Republic's Barbora Krejcikova beat Kazakh opponent Zarina Diyas, who retired in the first set after trailing 2-5, Switzerland's Belinda Bencic beat Jessica Pegula 6-3, 6-3 and Anastasia Pavlyuchenkova of ROC thumped Italy's Sara Errani 6-0, 6-1. Maria Sakkari of Greece and Elena Rybakina of Kazakhstan also won their -round matches in straight sets. Marketa Vondrousova of Czech Republic had a tough outing against Kiki Bertens of the Netherlands, winning in three sets, 6-4, 3-6, 6-4. /IANS