BEIJING — Hwang Kyung-seon won South Korea's third gold medal in taekwondo on Friday while Hadi Saei of Iran captured the men's 80-kilogram class after an upset sent favorite Steven Lopez of the United States to a quarterfinal loss.

Lopez, the defending Athens gold medalist, came back to take bronze.

Saei, who won the gold in a lower weight class in Athens, went ahead in the first round against Italy's Mauro Sarmiento, but Sarmiento hit him squarely with a head kick to take a 4-2 lead.

Saei landed a kick in the second round to move within a point, then another to Sarmiento's side to tie the score 4-4 going into the final round. He came out quickly in the third, scoring another point for the lead and added on a sixth point to seal the victory.

Lopez scored on Azerbaijan's Rashad Ahmadov in the final seconds to win bronze. The second bronze went to China's Zhu Guo, who defeated Britain's Aaron Cook 4-1.

Saei moved easily through his group, taking his first match with a 7-point margin, then winning 3-2 over China's Zhu and 4-1 in the semis against Ahmadov.

Sarmiento — coming off a leg injury that has slowed him since 2006 — narrowly made it to the semis by defeating Lopez in a quarterfinal that went into overtime.

Lopez, who hadn't lost a bout since 2002, was the heavy favorite.

Lopez fought Bahri Tanrikulu of Turkey in his opening bout, a rematch of their final in the Athens Games.

After a scoreless first round, Tanrikulu, a two-time world champion, hit with a roundhouse kick with 20 seconds to go in the second round to take the lead. Lopez came back at the start of round three to score two points and added another to go ahead 3-1. Tanrikulu had a point deducted just before the bell and the match ended 3-0 for Lopez.

But Lopez's luck then ran out.

He led 2-0 going into the final round of the quarters, but was scored on and then dropped a point for a penalty to go into overtime with Sarmiento. With time running out, Sarmiento nailed Lopez with a jumping kick as Lopez lunged forward.

The U.S. team protested the point deduction in the third round, saying it was a legal defensive move and not an illegal chop kick, but the protest was not accepted.

"We were manhandled, we were threatened not to protest, but we continued out of good faith," said team leader Herb Perez. "We don't feel we were given a level playing field."

In Friday's women's final, Hwang defeated Canada's Karine Sergerie with a kick in the final seconds to win the women's 67-kg class.

Hwang, launching few attacks, trailed Sergerie by a kick as the first round ended, but came back with 30 seconds left in the second round to tie it up. She scored with a back kick with 35 seconds left to win.

Hwang, who was the Athens bronze medalist and world champion in 2005 and 2007, cruised through her opening bout with a 5-1 score.

She fought a cautious quarterfinal but went ahead in the second round and used a counterattack kick in the third to win 3-1. In the semi, she squared off with longtime rival Gwladys Epangue of France. She won in overtime.