Former World Championships silver medallist N Usha suffered a shock quarter-final defeat even as India [ Images ] were assured of eight medals in the Asian Women's Boxing Championships in Astana, Kazakhstan.

Usha, who was expected to have it easy against Chorieva of Tajikistan, a country participating for the first time in the event, was knocked out in the lightweight 60kg category.

After the opening two minutes ended 0-0, Usha was on the backfoot in the second round, with Chorieva taking a 2-0 lead. She fought back to make it 3-3 in the third round and the two were tied 4-4 for most part of the final round as well.

But, with 20 seconds left on the clock, Chorieva landed a scoring punch to leave the Indian camp stunned.

"It was not expected. Usha was the hands down favourite, but just a few seconds before the end she lost the bout. It's very disappointing," said Indian Boxing Federation secretary-general P K Muralidharan Raja, who is in Astana as a technical delegate.

Priyanka Chaudhary (54kg) clinched victory by the smallest of margins, beating Minova Ayako of Japan [ Images ] after fighting out a tense quarter-final bout.

Priyanka was tied 1-1 with Ayako in the opening round. She nosed ahead to 2-1 in the second but Ayako fought back to make it 3-3 at the end of the regulation four rounds.

The Indian was declared winner after accepted individual scores put her 7-5 ahead of her opponent.

Pavitra (57kg), on the other hand, had no trouble getting past another Japanese Kugimiya Tomoko 11-2. The Indian led all through the bout and was never troubled by her rival.

Earlier, four-time world champion M C Mary Kom (46kg), L Sarita Devi (51kg), Sonam Yadav (75kg) fought their way to the semis, while Kavita Goyat (69kg), Aswathi Mol (81kg) and Kavita Chahal (+81kg) got byes into the last-four stage.

India has sent an 11-strong team for the event, which has 16 countries participating.