ST. PETERSBURG, Russia (AP)—Third-seeded Janko Tipsarevic of Serbia and eighth-seeded Victor Hanescu of Romania advanced to the second round of the St. Petersburg Open with straight-sets victories on Tuesday.

The 46th-ranked Tipsarevic beat two-time semifinalist Igor Kunitsyn of Russia 6-4, 6-2. Hanescu ousted 2009 runner-up Horacio Zeballos of Argentina 6-2, 6-0 in 54 minutes.

Tipsarevic, who lost to eventual champion Andy Murray in the quarterfinals in 2008, broke the 106th-ranked Russian three times. He served seven aces, hit 10 winners and lost only five points in his nine service games to win in one hour and four minutes.

“A break in the opening game gave me confidence,” said Tipsarevic. “Serve is my key weapon and I really served well today.”

Tipsarevic will face American Michael Russell in the second round on Wednesday.

The 52nd-ranked Hanescu, the 2008 semifinalist, won eight consecutive games at one stage and never faced a break point.

Hanescu will next play American qualifier Rajeev Ram, who served 17 aces to beat Pablo Andujar of Spain 6-3, 6-7 (5), 6-3. The 166th-ranked Ram advanced to the second round of an ATP tournament for the first time since losing to Andy Roddick in Atlanta in July.

Earlier, sixth-seeded Denis Istomin of Uzbekistan retired with a right knee injury while trailing Illya Marchenko of Ukraine 6-2, 2-2.

“I had no time to recover after playing in the Kremlin Cup,” said Istomin, who beat Marchenko in the first round on the way to the semifinals in Moscow last week. “I felt constant pain in my knee and decided not to aggravate it as I still have two tournaments ahead to collect points.”

Also on Tuesday, Paul-Henri Mathieu of France advanced with a 6-4, 6-3 victory over Maximo Gonzalez of Argentina, while qualifier Evgeny Donskoy scored his first victory in an ATP event, beating his fellow Russian wild card Andrey Kuznetsov 7-5, 7-6 (2).