Varvara Lepchenko came through the opening round of the Bol Open as Anna Tatishvili joined her on Tuesday.
American second seed Lepchenko claimed a 6-1 7-5 victory over Croatian local and wildcard Ana Vrljic on the first day of main-draw action.
Tatishvili had it far tougher at the WTA 125K series event, taking over two and a half hours to edge past Paula Kania.
The Georgia-born American completed a 6-4 6-7 (4-7) 7-5 win on the clay courts.
The only seed to fall was Patricia Maria Tig as the Romanian was comprehensively beaten 6-2 6-1 by Jennifer Brady.
Wildcard Ipek Soylu made the most of her opportunity in a rollercoaster 6-3 0-6 6-1 win over Julia Glushko.
In a battle between qualifiers, Bulgarian Elitsa Kostova was a 6-1 7-6 (7-4) victor against Ekaterina Alexandrova.
Serbian Ivana Jorovic overcame Isabella Shinikova 7-5 6-2, Stefanie Voegele beat Andreea Mitu 6-3 6-2 and Sachia Vickery was a 6-2 7-5 winner against Tena Lukas.