New Delhi: Teen sensation L Devendro Singh (49kg) and Commonwealth Games gold-medallist Manoj Kumar (64kg) booked their Olympic berths by advancing to the World Boxing Championships' quarter-finals with contrasting wins in Baku, Azerbaijan on Tuesday.

While Manoj rallied to defeat China's Qing Hu 17-15, 19-year-old Devendro continued his giant-killing spree by beating seventh seed Carlos Quipo of Ecuador 18-12 in another impressive performance.

The duo has sealed berths for the Olympic Games, becoming the first lot of Indian boxers to qualify for the mega-event.

Top 10 boxers (from 49kg to 81kg) will make the Olympic cut while boxers in the 91kg and +91kg category will have to finish among the top-six to book their London tickets.

But there was some disappointment too for India as Asian Games silver-medallist and 12th seed Dinesh Kumar bowed out with a 7-16 loss to CWG gold-medallist Damien Hooper of Australia.

Manoj was the first to take the ring for India and the counter-puncher, who has won the coaches' admiration for his calculative approach and adaptability, once again impressed with a composed performance.

The Haryana-boxer was trailing 3-6 in the opening round but he bounced back brilliantly be level 7-7 in the second round and narrow the overall gap to 10-11.

He went on the offensive in the final round, securing seven points against his rival's 2 to clinch victory. Manoj will now face fifth seed Thomas Stalker of England. Stalker, a European Championship silver-medallist, defeated Russia's Alexander Solyanikov 17-9.

Next up was the spunky Devendro and he once again displayed nerves of steel against his more fancied rival.

The nimble-footed teen from Manipur took a 5-2 lead in the opening round, capitalising on his opponent's overtly defensive approach with some telling body blows.

"I was under immense pressure before this bout. It was once in a lifetime opportunity I did not want to miss and I think it helped me in the end to strain myself a bit before the bout," Devendro said.

Although his rival became more aggressive in the next two rounds but Devendro managed to negate that with his precise straight body blows and hooks to seal the issue comfortably.

"I had fought with him during our recent training trip to France where he was among those I sparred with. That gave me a good idea of his game and it helped me in this bout," he said.

Devendro will next face Korea's Shin Jong Hoon, who defeated France's Jeremy Beccu 22-10.

But Dinesh's loss came as a dampener in the day session of the mega-event as he paid the price for relying too much on power then movement against an agile rival, who impressed with his ring craft and reflexes.