BEIJING — China's world champion Wu Jingyu won the women's under 49-kilogram class on the first day of the Beijing Games taekwondo competition Wednesday, and Afghanistan got its first Olympic medal, winning a bronze in men's under 58-kg.

Mexico's Guillermo Perez won the men's under 58-kilogram gold in a decision over Dominica's Yulis Gabriel Mercedes. Aghanistan's Rohullah Nikpai won one of the two bronzes for men — and his country's first Olympic medal ever.

China's Wu took the lead in the first round of the women's final with a chest kick to Thailand's Buttree Puedpong. She narrowly missed on a high kick to Puedpong's head late in the second round that hit the Thai in the shoulder and sent her to the mat.

Puedpong had a point deducted in the third round, putting her in negative territory, and Wu held on for the win.

Wu also cruised through the preliminaries, beating her first opponent with a 7-point margin, and going ahead 4-0 in her quarterfinal against Sweden's Hanna Zajc at the end of the second round. She scored with a head kick — worth two points — early in the third round, and then another that knocked Zajc down and ended the bout at 8-1.

The win set up a semifinal between Wu and the other favorite in the division, Taiwan's Yang Shu-chun, the 2007 world bronze medalist.

Yang started her quarterfinal with a flying back kick against Iran's Sara Khosh Jamal. She had the point deducted in the third round for a penalty but won with a head kick in overtime that sent Khosh Jamal to her back.

But in the semifinals, Wu took the lead with a solid looping head kick and a midsection kick to close the first round. Yang scored in the second round, but Wu matched that early in the third. Wu won 4-1.

Venezuela's Dalia Contreras Rivero and Puedpong went into overtime in the other semifinal. Neither was able to score, and Peudpong was declared the winner by the judges.

Contreras Rivero and Cuba's Daynellis Montejo, who defeated Yang, took the bronzes.

Charlotte Craig of the United States lost in the quarterfinal.

Craig began her first Olympics with a body kick against Switzerland's Manuela Bezzola. She scored two more in the opening round and another in the third to win her first bout 4-0.

In the quarterfinal, the 17-year-old fought Rivero, who beat her in the 2008 Pan-Am Games.

Both were wary and took penalties for passivity, then traded kicks to end the first round at 1-1. Her opponent went ahead in the second round with a front kick, then scored again to widen the gap. Craig added a point at the end of the round, and took the fight to the Venezuelan in the third but failed to find an equalizer.

"This is more of a learning experience," she said. "I was lucky to make it to these Olympic Games — 2012 will be different. Even though I'm 17 years old, I'm still one of the top athletes in the world. I just have to believe in myself."

Mexico's Guiliermo Perez had to go the distance with Mercedes in the men's final.

He scored early, but Mercedes came back with seconds left to force the match into overtime. Neither could score in the alloted two minutes, and the judges' decision went to Perez.

Defending Olympic champion Chu Mu-yen of Taiwan got off to a flying start in the preliminaries, using an airborne back kick and then a downward chopping head kick to open a 3-0 gap against Kenya's Dickson Wamwiri. He added two more in the second and third rounds to end the match at 7-0.

But his momentum ran out in the quarters.

Chu was quickly forced to play catch-up after Mercedes pegged him with a body kick combination. Chu evened it up in the second round at 2-2, but fell behind again as time ran out.

World champion Juan Antonio Ramos of Spain, who finished fourth in Athens, also struggled in the quarterfinals, going into the third round tied with Marcio Ferreira of Brazil. He scored, then lost a point for a penalty and the match went into overtime. He won with a body kick after 20 seconds.

In the semifinal, Ramos trailed Mercedes at the start of the final round, but Mercedes lost a point on penalties, sending that match into overtime as well. Mercedes scored the winning kick with just six seconds remaining.

Afghanistan's Nikpai defeated Ramos in the bronze medal match. The other bronze went to Taiwan's Chu.