Amit Panghal secured a hard-fought 3-2 triumph over Olympic champion Hasanboy Dusmatov, whom he had also beaten to claim the Asian Games gold just a few months ago.
Kavinder Singh Bisht (56kg) upstaged reigning World champion Kairat Yeraliyev, while Amit Panghal (52kg) edged past familiar foe and Olympic champion Hasanboy Dusmatov, assuring themselves of medals at the Asian Boxing Championships, in Bangkok, on Monday.
In the women's draw, world silver-medallist Sonia Chahal (57kg) advanced to the last-four stage at the continental showpiece.
Bisht clinched a split verdict over Yeraliyev, who hails from Kazakhstan, in a high-intensity contest to assure himself of a maiden Asian championship medal.
Panghal, who claimed a bronze in the 2015 edition of the event, also secured a hard-fought 3-2 triumph over Dusmatov, whom he had also beaten to claim the Asian Games gold just a few months ago.
Before that, the two boxers had also clashed in the World championship quarters where Dusmatov had emerged triumphant.
Sonia too fetched a similarly close victory over Korea's Jo Son Hwa.
Also making the semis was national champion Deepak Singh (49kg), who did not have to step inside the ring to fight for the spot after Afghanistan's Ramish Rahmani gave him a walkover owing to injury.
However, World championship bronze-medallist Lovlina Borgohain (69kg) bowed out of contention after a quarter-final loss to reigning World champion Chen Nien-Chin of Taiwan.
The highlight of the day was Bisht, who came into the tournament after a gold medal at the GeeBee Tournament in Finland. The boxer from Uttarakhand showed tremendous grit against a tough opponent.
Yeraliyev succeeded in drawing Bisht into a trap in the opening three minutes of the bout but the Indian fought back hard in the next two rounds.
Bisht fought mostly with a shell guard and managed to thwart Yeraliyev's relentless attacks.
By the second round, the Kazakh, who is a two-time bronze-medallist at the event, dropped his guard. Although Yeraliyev seemed the quicker of the two, Bisht was managing to outmanoeuvre him quite comfortably.
Yeraliyev was also a bronze-medallist from last year's Asian Games.
Sonia also endured an exhausting bout against Hwa but came out trumps. The fast-rising boxer from Haryana struck some clean jabs in her thrilling win.
In the evening session, Panghal and Dusmatov had the crowd on its feet with an engrossing showdown. The Armyman from India dominated the opening round with powerful uppercuts and jabs.
Dusmatov came back strongly and was quite impressive in the second round but the resolute effort was not enough to find favour with the judges.
In another women's bout, Seema Poonia (+81kg) lost to China's Yang Xiaoli 5-0, ending another disappointing international outing for her. Poonia had got a bye into the quarters.
In the last Indian bout of the day, Rohit Tokas (64kg) fought hard but could not avert a 2-3 loss to Mongolia's Chinzorig Baatarsukh in the quarter-finals.
