London, Aug 7 (IANS): MC Mary Kom ensured India's best medal haul at the Olympics by reaching the women's boxing semifinal at the London Games while Beijing bronze medallist Vijender Singh failed in his bid to become the first Indian to win back-to-back medals at the Olympics by losing his quarterfinal bout.

Vijender made a heartbreaking exit after going down 13-17 to Uzbek Abbos Atoev in the men's 75kg quarterfinal at the ExCel Arena late Monday night.

Having been beaten by Vijender 7-0 in the final of the 2010 Asian Games, the Uzbek was determined to take revenge this time.

The two boxers took time to get the measure of the other in the first round that ended 3-3.

The crowd was completely behind the Indian as chants of "jitega jitega India jitega" reverberated in the arena.

In the second round, the Indian was slow off the blocks, allowing Atoev to take a two-point lead by winning the round 7-5. Atoev's made his flurry of punches count and Vijender also hit back with an upper cut that disbalanced the Uzbek.

The Uzbek was more tactical in the second round that helped him to take a crucial lead. Vijender with a left hook tried to breach Atoev's defence, but it was not his day.

In the third and the final round, Atoev displayed some lovely defensive skills as Vijender ran out of steam.

Mary Kom, a mother of twins, thrashed her Tunisian rival Maroua Rahali 15-6 in a one-sided quarter-final. She is assured of a bronze even if she now loses her semi-final against Nicola Adams of Britain. Both losing semi-finalists are awarded bronze in the competition.

The 29-year-old Manipuri's exploits made sure India will return home with a better medal tally than its previous best of three (one gold and two bronze from Beijing. Pistol shooter Vijay Kumar has bagged a silver, and rifleman Gagan Narang and women's shuttler Saina Nehwal a bronze apiece in the Games so far.

"It feels great to win an Olympic medal for the country. But I want to carry on the momentum or a bigger medal," Mary Kom said.

Asked about her chances in the semis against home favourite Adams, Mary Kom said: "She is a good boxer. I lost to her in the World Championship quarter-final by just two points. Boxing is a very tough sport and winning or losing is a part of the game. But I will give my best."

In track and field, male discus thrower Vikas Gowda, considered the country's best bet for a medal from the discipline, qualified for the final by hurling the metallic disc to a distance of 65.20 metres in his second attempt to make the cut. The US-based Indian has a best throw of 66.28m.

It was curtains on India's shooting campaign at the Olympics with rifle shooters Narang and Sanjeev Rajput and trap exponent Manavjit Singh Sandhu failing to qualify for the final rounds of their respective events here at the Royal Artillery Barracks.

Narang, who won the bronze in men's 10-metre air rifle, and Rajput finished 20th and 26th, respectively, in the 50m three-position event.

For Sandhu, a former World Champion, it was disappointment again for the third time as he finished 16th in the qualifiers and missed the final cut.

But it has been a highly successful campaign for Indian shooters.

Besides Narang and Kumar, another rifle shooter, Joydeep Karmakar finished fourth and missed the bronze only by a whisker.