The winners of the two semi-finals compete for the gold medal while the losing semi-finalists are awarded a bronze each.
The Indian, a five-time World Champion, put in a dominant performance. But her style Monday was in stark contrast to her performance Sunday, when she beat Karolina Michalczuk of Poland.
In the first round, she sized her opponent and relied heavily on defensive tactics. She time and again tried to get inside of her opponent to land a punch but the Tunisian was able to keep her distance.
Both fighters did not throw many punches and the round ended 2-1 in the Indian's favour.
The second round, too, was similar as the diminutive Indian tried to keep away from her taller opponent. Relying on one-off punches, Mary Kom frustrated her opponent with her quick evasive measures.
Fighting conservatively, Mary Kom still was narrowly able to edge out her opponent 3-2.
Image: India's Mary Kom celebrates after defeating Tunisia's Maroua Rahali in a women's flyweight 51-kg quarterfinal boxing match at the 2012 Summer Olympics, Monday, Aug. 6, 2012, in London