In a notice issued late Thursday, the Public Security Ministry said it ordered police nationwide to step up efforts to "resolutely prevent such crimes from occurring".

Earlier this week, a Chinese microblog account made waves by successfully helping a young father find his six-year-old son, who was kidnapped three years earlier. At least six other children have been similarly rescued, reports said.

The microblog, set up on leading portal Sina.com by a professor known for championing the rights of China's huge underclass, encourages people to snap pictures of child beggars and orphans and upload them to the site.

Chinese microblogging services allow users to send 140-character messages similar to those seen on Twitter, which is blocked in China by government censors.

Unlike Twitter, however, microblog users in China also can embed photos in a posting.

The episode has underlined the rapidly growing power of the online community to influence government actions in areas such as abductions, a problem that state media say is linked to China's "one-child" policy.

The traditional preference for a male heir to carry on the family name remains strong in China, and the population-control policy has contributed to kidnappings by families desperate for boys, reports say.

The police ministry ordered law-enforcement officials around the country to work closely with other government agencies in a "concerted and multi-pronged approach to step up the crackdown and rescue work, and protect the legal rights and interests of minors".

It also told police to obtain DNA samples of young beggars on the street whose origins were unknown and enter them into a nationwide database.

Hopeful parents of missing children have seized on the microblog, which had more than 200,000 followers as of Friday up from 150,000 just a day before.

The account was set up in late January by Yu Jianrong, a professor of rural development, and a frequent critic of government indifference to the needs of China's huge poor working class and rural farmers.

Abductions and human trafficking have become serious public concerns after a string of revelations, including a shocking 2007 scandal in which thousands were forced into slave labour in brick yards and mines across the nation.

Mounting outrage led to a government crackdown but the problem