BEIJING — South Korea collected two gold medals in taekwondo on Thursday, while siblings Mark and Diana Lopez of the United States won a silver and a bronze.

Son Tae-jin scored a kick in the final second to defeat Mark Lopez for the gold medal in the men's 68-kilogram competition, and Lim Su-jeong beat Turkey's Azize Tanrikulu in the women's 57-kg.

Lopez — who is competing in Beijing with Diana and older brother Steven — fell two points behind as Son displayed superior kicking in the first round of the final. Lopez, the 2005 world champion, came back with a score in the second round and Son had a point deducted for passivity, evening the score at 1-1.

A low kick sent Son to the mat in the third round, and when he got up both fighters traded kicks, bringing the score to 2-2. Son then scored with one second remaining to take the gold.

Lopez said he thought he had gotten a kick in at the same time.

"He threw a kick and I threw a kick and in my humble opinion I thought it should have been 1-1," he said. "But I respect the judges' decision in giving him a point and not me. ... It's a subjective sport."

"I came up short," he added. "I am going to start training for 2012 and hopefully I will get my gold medal then."

Son, who beat Lopez in the quarters of the 2007 World Olympic qualifier, narrowly defeated Turkey's Servet Tazegul to earn his semifinal slot against Sung Yu-chi of Taiwan. In a furious kicking match, Son won that bout 7-6.

He showed little sign of fatigue in the final, however, and warded off several powerful barrages from Lopez.

Taiwan's Sung and Tazegul of Turkey took the men's bronzes.

In the women's final, Lim and Tanrikulu opened slowly, and Lim had a point deducted for passivity. Lim, the 2007 Universiade champion, scored a kick in the second round to even it up going into the third round and scored the winning back kick with 20 seconds left.

Lim cruised through the preliminaries and scored three times in the final round of her quarterfinal to make the semis against Italy's Veronica Calabrese, the winner of the 2008 university championships.

"I am very proud to be a Korean today," Lim said.

A favorite going into the competition, Diana Lopez fell behind Tanrikulu, who hit her with a roundhouse kick to the chest in the quarterfinal. Tanrikulu, who also has a brother, Bahri, in the competition, had the point deducted on a penalty in the second round, bringing them scoreless into the third.

They traded points at the outset and neither was able to score again until Tanrikulu hit the winning kick after 34 seconds of overtime.

"I should have pressed her harder in the first round," Lopez said.

Lopez trailed Calabrese in the final round of the second bronze medal match but evened it at 2-2 to force it into overtime. Lopez pegged Calabrese after 25 seconds to take the medal. Taekwondo awards two bronze medals in each weight division.

The second went to Martina Zubcic of Croatia.

South Korea, where taekwondo originated, has now won at least a bronze medal from all 10 of the athletes it has entered in the Olympics. Taekwondo became an official Olympic sport in Sydney in 2000.

Though the Koreans are perennial favorites, the Lopezes have stolen some of the spotlight.

They are the first three siblings to compete for the United States in the same Olympics since the gymnast Tritschler brothers, who competed in St. Louis in 1904 but failed to medal.

Counting coach Jean, their eldest brother, they are the first four siblings to participate together in Olympic history, according to the World Taekwondo Federation.

In 2005, they became the first three siblings to win world championships in the same sport in the same year.

"It's a great day for the Lopez family," Jean said.

Steven, who hasn't lost a bout since 2002, defends his title from Athens on Friday. He also won gold in Sydney, but in a lighter weight class.