Olympian Shiva Thapa and Asian silver-medallist L Devendro Singh entered into the semifinals at the Senior Men's National Boxing Championships being played in Guwahati.Two-time Olympian and local favourite Shiva defeated Ashok from Uttar Pradesh in a unanimous decision in 60 kilogram category. In fly weight, L Devendro Singh, representing Manipur, had to toil hard against Haryana's Niraj. The 24-year-old boxer eked out a 3-2 win in a hard-fought contest.Among others, former Commonwealth Games gold medallist Manoj Kumar who is representing RSPB, outclassed Jammu and Kashmir's Ashish 4-1 to reach the final four.In welterweight 69kg category, Ankush Hudda of Chandigarh thrashed Andy Chauha of Mizoram 5-0, Delhi boxer Prayag Chavhan also emerged victories over Manish of Madhya Pradesh to enter 122 kg semis.