Fifth seed Filip Krajinovic made a comfortable start to his Sofia Open campaign on Wednesday, defeating Alexandar Lazarov 6-0 6-3.

Krajinovic was the only seeded player in action and he was dominant against home hope Lazarov, who is ranked 462 in the world.

The Serbian swept the first set without conceding a break point and finished the job by claiming the last four games in the second despite Lazarov putting up more of a fight.

Elsewhere, Krajinovic's compatriot Miomir Kecmanovic crashed out to Italian Gianluca Mager, who fired down 11 aces and forced 10 break-point opportunities to earn an impressive 7-6 (7-3) 6-3 win.

Australian James Duckworth, meanwhile, had to launch a comeback before ultimately prevailing 3-6 6-4 6-4 against Finland's Emil Ruusuvuori to book a round two match with Benoit Paire.

The number one seed and defending champion Jannik Sinner will begin his campaign on Thursday with a last-16 contest against Egor Gerasimov.

Second seed Gael Monfils will play Ilya Ivashka, who defeated Pablo Andujar in straight sets, with the winner to face Mager, who is the first man in the quarter-finals.

Alex de Minaur will also be in action against American Marcos Giron.