China's Zhenye Xie turned in a powerful performance in the last of the sprint events at the Youth Olympic Games

He held off a strong challenge from Japan's Keisuke Homma to win the boys 200m at Bishan Stadium.

Xie, who celebrated his 17th birthday on Tuesday, was well placed throughout, and despite the closeness of the times - he clocked 22.22sec to Homma's 22.27 - never looked in serious danger in the closing stages. The bronze medal went to Germany's Patrick Domogala in 21.36.

Earlier in the day, Nkiruka Florence Nwakwe completed a girls sprint double for Nigeria when she stormed to victory in the 200m final less than 24 hours after her compatriot Josephine Omaka had taken gold in the 100m.

Nwakwe, who crossed the line with a celebratory wave, sees her win as a major stepping stone to an international career. "I was no one. Now I am someone," she said. "This means a lot to me and everyone who has supported me."

The basketball semifinals brought some of the most dramatic action of the day, with Australia's girls beating the strongly fancied Americans in extra time to advance to the final on Monday against China and the Croatian and Serbian boys' teams winning their semifinals to set up what amounts to a derby final, also on Monday.

The Australian girls came back from eight points down at halftime to tie the regulation-time score at 20-20 and send the game into overtime, in which their captain, Olivia Bontempelli, clinched victory by nailing two free throws and leaving their rivals distraught, with one of the American girls collapsing on the court in tears. Somewhat less dramatically, China beat Canada 28-21 in the other girls' semifinal.

There was also bitter disappointment for America's male basketball players, who went down 34-29 to Serbia in overtime, while Croatia beat Greece 33-30, also in extra time.

A strong all-round performance by Korea's Kim Dae Beom brought him gold in the boys' modern pentathlon. Kim, who finished seventh in fencing in the first of the event's three disciplines, climbed up the table with a third place in swimming, but was still well behind the youth world champion Han Jiahao of China, the favourite for gold. Han, however, could manage only 15th position in the final discipline, the run and shoot, in which Kim's second place was enough to secure the gold.

There was a dramatic finish in the gold medal final in the men's junior 10m air rifle competition, with China's Gao Ting Jie edging out Illia Charheika of Belarus with his final shot of the tournament. Gao, who caused an upset in the senior ranks earlier this year when he took a silver medal at the International Shooting Sport Federation World Cup, scored a 10.5 against his rival's 9.4 to finish with a points total of 694.9, just 0.8 ahead of Charheika.

The Games' cycling competitions wound up with a victory for Belgium's Boris Vallee in the junior men's road race and a gold medal for Colombia in the mixed team event.

Vallee, who pounced in the final lap of the 48km road race, immediately called his parents in Belgium and broke down in tears.

"I had to cry all the time," he said. "This is for all my family and friends."

The road race - which was also the final event for the mixed teams - brought just as much joy for the three boys and one girl of the Colombian team, who had been in a commanding position after victories in the men's junior cross-country and men's junior BMX and performed strongly enough on Sunday to clinch the gold.

In the boys long jump, Brazil's Caio Dos Santos stormed back after a shaky start to snatch victory with his final leap of 7.69m. Dos Santos, who failed to complete either of his first two attempts successfully, held his nerve in the final round of jumps to edge Japan's Matsubara Sho (7.65m) into second place.

Ethiopia, a traditional middle distance powerhouse, took gold in the boys 1000m when Mohammed Geleto timed his finishing burst to perfection, breaking out of the pack down the back stretch to close in on Ireland's Mark English and storm into the lead coming out of the final bend. Geleto crossed the line just over two seconds ahead of Qatar's Hamza Driouch, who also finished strongly.

Olympic double gold medalist Zsolt Gyulay, who has been advising the Hungarian canoe/kayak team in Singapore, was rewarded by seeing two of his young compatriots, Sandor Totka and Ramona Farkasdi, paddle to gold medal victories in the boys' and girls' K1 canoe sprints at Marina Reservoir. "These guys are still young. They're children, so we have to show them," said the delighted Gyulay.

Sunday's other gold medal winner in the canoe/kayak events was Cuba's Osvaldo Orestes Sacerio Cardenas, who held off a fierce challenge from Ukrainian rival Anatolii Melnyk in the boys' C1 sprint.