Stanislav Manolev scored his second goal in the 2014 World Cup qualifying campaign as Bulgaria laboured to a 1-0 win over Armenia in a Group B match on Tuesday featuring three red cards.
The only goal came two minutes before the interval when Manolev, who also struck in Friday's 2-2 draw at home to Italy, turned in a cross from captain Ivelin Popov who had dribbled past 39-year-old right back Sargis Hovsepyan.
Bulgaria almost doubled their lead in added time as substitute Dimitar Rangelov was thwarted by advancing Armenia goalkeeper Roman Berezovsky.
Earlier, a dozen players were involved in a 73rd-minute fracas during which Bulgaria's Svetoslav Dyakov was shown a second yellow card and Armenia substitute Marcos Pinheiro was also sent off.
Armenia, who rarely looked like scoring, finished the game with nine men after Gevorg Gazaryan was dismissed for pushing a ball boy in the 77th minute.
Bulgaria's current team are a long way from the one that reached the 1994 World Cup semifinals in the United States but recent performances have shown signs of promise.
"I expected to win six points from our first two qualifiers and I think we deserved to have six points because we played very well," said Bulgaria coach Luboslav Penev.
"But don't get me wrong, nothing has changed and Italy remain favourites for the first place.
"I'm pleased with today's victory," Penev added. "Armenia are a tough and well-organised team. They're really fast with the ball and they can be very dangerous."
Bulgaria, who have four points from two games, host Denmark in their next qualifier on October 12 while Armenia (three points) entertain Italy.
"I would like to apologise for my players' behaviour and for Gazaryan's reaction," Armenia coach Vardan Minasyan said. "We came here to win but we're nervous and we made mistakes."