Poland beat Bulgaria 3-1 (25:14, 23:25, 25:22, 25:23).
Poland, the defending champions, secured victories in all five matches in the group round.
The Polish team last week beat Finland 3-1, notched up a comfortable 3-0 win over Puerto Rico, and defeated Cuba 3-1. In their fourth match on Monday, Poland beat Iran 3-0, guaranteeing a spot in the second round of the championships.
The Poles, managed by Belgian coach Vital Heynen, are set to take on Argentina, Serbia and France in pool H matches, which run from September 21 to 23.
Second-round winners in four groups and two teams with the highest scores will move on to the third round.
The 2018 FIVB Volleyball Mens World Championships run until September 30, with the Final Six scheduled to be held in Turin, Italy.
The FIVB volleyball federation is the sports international governing body.
(aba/vb)
Source: PAP