The emotional meeting of a man in southern China and a young boy believed to be his missing son has drawn fresh attention to the country's problems with child abductions and to new efforts to use the Internet to find lost children.

Peng Gaofeng had been searching for his son Wenle since 2008, when the boy, then three years old, disappeared from a public square near Mr. Peng's small payphone shop. Earlier this month, his family got a tip from an Internet user saying he saw a boy resembling Wenle in photos posted online, and on Tuesday Mr. Peng was united with the child—who had been in the care of a supposedly adoptive father who died last year. "I knew it was him immediately, though he didn't recognize me at first," a jubilant Mr. Peng said in a telephone interview Wednesday.

Details of the case remain unclear and a DNA test is pending. Local police couldn't be reached for comment. But video of Mr. Peng's tearful meeting with the boy, filmed by a Chinese journalist, has become a nationwide sensation on China's Internet and in local media.

The incident has put a spotlight on widespread problems with child abductions in China, where state media reports have said there are thousands of human-trafficking gangs and where many kidnapped children have been sold to other families or forced to participate in organized begging rings in big cities, a phenomenon also relatively common in the Middle East, Africa, and elsewhere in Asia.

In 2007, a report by Hong Kong-based Phoenix Television Corp. said 200,000 children go missing in China every year. In the U.S. in 2009, the latest data available, there were 558,493 missing persons reported under the age of 18, according to the Federal Bureau of Investigation's National Crime Information Center.

Mr. Peng's case has also highlighted a growing effort by private citizens to find missing children with the help of social networking websites and other online tools. That effort has gained momentum in recent years as China's population of Internet users has mushroomed: It now has more than 450 million Internet users, by far the most of any nation, according to government statistics.

Last month, Yu Jianrong, a prominent scholar who researches rural development, started a microblog account for Internet users to post pictures of children begging in cities to help connect them with their parents. Mr. Yu told the state-run Beijing Daily newspaper in an article published Wednesday that four families have contacted him saying that photos on the microblog resemble their missing children. It hasn't been confirmed yet if any are actual matches.

Clear statistics aren't available on child abductions in China, so it's not known if the problem is getting worse. But it has gained growing attention from the Chinese public thanks to a spate of high-profile cases and government crackdowns. The response has been somewhat reminiscent of the reaction in the U.S. to prominent cases of missing children that sparked new legislation and other efforts in the 1980s to find missing children.

In December, authorities in the province of Guizhou said they had broken up 47 human-trafficking rings in a two-year campaign, rescuing 151 children and 209 women. Overall, according to China's state-run Xinhua news agency, between April and September of last year police freed 5,896 children who had been abducted and sold for profit. Chinese police have set up their own website to help parents find missing kids, though it's unclear how effective it has been.

Mr. Peng's case has elicited an outpouring of emotion. One user at online video website Ku6 Media called for state broadcaster China Central Television to start an exclusive channel for child trafficking. Many comments demanded the death penalty for anyone caught trafficking children. "China's law and punishment on this is too light," wrote a user named Hzh18918. "Abduction is worse than murder."

When Wenle disappeared, Mr. Peng and police conducted a frantic search, uncovering a surveillance video showing the boy with a man wearing a black leather jacket. The family turned their small business into a search center, and offered a reward of 100,000 yuan ($15,197)—a huge sum for average Chinese—for information on his whereabouts.

Mr. Peng was interviewed about the case by Deng Fei, a reporter for Phoenix Weekly magazine, who later posted Wenle's photo on Sina Weibo, a Chinese Twitter-like microblogging service. Thousands of users reposted the photos.

After several fruitless tips, someone identifying himself as a student at Jiangsu University—some 1,200 kilometers, or roughly 700 miles, from Shenzhen—said Feb. 1 that he saw a boy strongly resembling Wenle in a nearby village. The student sent a photo to Mr. Peng, who contacted police as soon as he saw the likeness to his son. He traveled with Shenzhen police to Jiangsu.

It isn't clear who took Mr. Peng's son or why, though Mr. Peng said he believes Wenle's abductor took Wenle home to raise as his own child, based on what he's been told by police, who could not be reached for comment. The man with whom the boy had been living in Jiangsu died of cancer last year, Mr. Peng said. Mr. Deng captured Mr. Peng's meeting with the boy on video. The father is shown standing nervously outside a police station waiting for the child's arrival, then breaking down in sobs after seeing him. The boy appears healthy and unharmed. Police officers stand by to soothe Mr. Peng as he calls his family and tells them "It's our boy."