Thursday's gathering at the Bulgarian national stadium in Sofia was organised through socal networking sites.
The event was specifically held on April 19 at 1919 local time (1619GMT) in a reference to Petrov's number 19 shirt at Villa.
Among the crowd were Bulgarian sports minister Suilen Neykov and the mayor of Sofia, Yordanka Fandakova.
After the singing of the national anthem a message of thanks from Petrov was read out to the cheering fans.
Petrov, who has 105 international caps, signed for Villa in 2006 after spells with CSKA Sofia and Scottish giants Celtic.
Source: AFP
Source: AFP