China filed an arrest warrant through Interpol for Yang, a senior official who oversaw construction projects in the booming eastern province of Zhejiang. She was eventually detained in Amsterdam in 2005, but nearly a decade on, China has yet to get her back despite protracted negotiations with the Netherlands.

Yang's case and others like it underscore the challenge for President Xi Jinping as he expands his already far-reaching anti-corruption campaign to tracking down suspects who have fled abroad, often taking their ill-gotten gains with them.

State media has been using the latest prong to Xi's crackdown - dubbed the "fox hunt" by the Ministry of Public Security in July - to warn officials about absconding.

But while China has extradition treaties with 38 countries, it doesn't have one with the Netherlands, or with the United States, Canada and Australia - the three most popular destinations for suspected economic criminals, according to state media.

Adding to the allure of those three countries for corrupt officials is suspicion there of Chinese law enforcement, said Chinese legal experts, along with the quality of life, world-class educational facilities and large ethnic Chinese communities.

Indeed, Western governments have long been reluctant to hand over Chinese suspects because the ruling Communist Party controls China's courts and torture can be used to extract confessions, the experts said. Capital punishment is also widely meted out, including for corruption.

"There are differences in our political systems as well as ideological differences," said Lin Xin, a researcher who specializes in international law at the Chinese Academy of Social Sciences, a government think tank.

"These differences will affect extradition."

Earlier this month, Chinese officials said more than 150 "economic fugitives", many of them corrupt officials, were in the United States. The government has given no recent overall figure for the number at large around the world.

Interpol has arrest warrants for 69 Chinese wanted on charges of corruption, embezzlement, fraud and bribery, according to a Reuters analysis of its public database.

Beijing has also grappled with so-called "naked officials" - government workers whose family members are overseas - and who use those connections to illegally shift assets out of China.

The sums of money believed to have been spirited out from all types of malfeasance are staggering. The Washington-based Global Financial Integrity group, a non-profit organization that analyses illicit financial flows, estimates that about $2.83 trillion flowed illegally out of China from 2005 to 2011.

Neither the Ministry of Public Security nor the Central Commission for Discipline Inspection, the party's anti-graft watchdog, responded to requests for comment.

"FOX HUNT" GATHERING PACE?

China has extradited 730 people suspected of major economic crimes from dozens of countries since 2008, the official Xinhua news agency said in July. In a sign the "fox hunt" might be picking up, 18 have surrendered or been extradited in the past month from places such as Cambodia, Indonesia and Uganda, Xinhua said.

But very few return from Western countries, said Liao Ran, a senior program coordinator of the Asia and Pacific department at Transparency International, a Berlin-based international corruption watchdog.

The most prominent is Lai Changxing, once China's most-wanted fugitive, who fled to Canada with his family in 1999 and claimed refugee status after saying allegations that he ran a multi-billion-dollar smuggling operation in the southeastern city of Xiamen were politically motivated.

After a Canadian court rejected Lai's application for refugee status, dismissing concerns he could be tortured or executed if sent home, Lai was deported, but not extradited, in 2011. He was jailed for life the following year.

David Matas, a lawyer who represented Lai in his refugee claim proceedings, said the case took so long because Canadian courts wanted to examine assurances from China that it would not execute or torture Lai.

Despite China's promises, Lai was skeptical since his brother and accountant had both died in jail, Matas said, adding the circumstances of their deaths were never fully explained.

"He was worried something like that could happen to him," Matas said by telephone from Winnipeg.

Chinese state media reported in 2009 that Lai's elder brother, Lai Shuiqiang, had died in prison in 2002 "after he suddenly fell ill". There were no articles about the accountant.

Prison officials did not respond to a request for comment.

U.S. TALKS

To help return fugitives in the United States, the Ministry of Public Security is trying to set up annual high-level meetings with U.S. authorities, the China Daily said on Aug. 11.

A spokesman for the U.S. Department of Justice said agency officials would meet Chinese counterparts in Beijing in December through the U.S.-China Joint Liaison Group on Law Enforcement Cooperation, adding the department regularly discusses law enforcement issues with China, including fugitives in both countries.  

The spokesman, Peter Carr, said both sides have occasionally returned fugitives when they were also subject to deportation under immigration laws, but declined to give specific examples.

In Canada, officials at various ministries including the Justice Ministry declined to comment on whether Chinese anti-graft investigators were in the country or planned to visit.

    In July 2013, the two governments concluded talks on a deal on sharing forfeited assets and the return of property. The agreement will not come into force until both sides ratify it. A Justice Ministry spokeswoman said she was not aware of Chinese officials in Canada trying to regain the proceeds of crime from corruption back home.

The Australian Attorney General's office said it was a long-standing practice not to confirm or deny if requests for assistance had come from foreign countries in investigations.

PROPERTY DEVELOPERS

Yang Xiuzhu worked her way up the ranks to become a deputy director of the construction bureau in Zhejiang province, according to Nanfengchuang, a magazine owned by the state-run Guangzhou Daily.

Local authorities said in 2004 she accepted kickbacks from property developers of more than 250 million yuan ($40.62 million), Xinhua has reported.

She was arrested in 2005 upon her arrival in the Netherlands, where Chinese anti-corruption and legal experts believe she remains. It was unclear why Yang flew there or whether she has a lawyer.

The Dutch Foreign Ministry said it would not comment on individual cases, although Dutch officials said there was no pending extradition request from China.

As recently as 2011, Xinhua reported that "the Chinese government is actively handling the extradition formalities" involving Yang.

STOLEN ASSETS

Recovering stolen assets might be easier for China as most nations want to stem the flow of corrupt money across borders, legal experts said, although some sums returned so far are paltry.

Australia for example has repatriated A$7.5 million to China since 2002 from embezzlement, fraud and money laundering, the Attorney General's department said.

"I think the U.S. is very, very serious about trying to trace and locate ill-gotten assets of politicos of any state who will seek to have the money returned," said Douglas McNabb, a D.C.-based veteran extradition lawyer.

Legal experts said China's best option for getting stolen assets would be through the U.N. Convention Against Corruption which obliges countries that have ratified it to cooperate.

The work could be time-consuming.

One example is a $3 million villa in the French Riviera that was a key piece of evidence in the corruption trial of Bo Xilai, the former high-flying Chinese politician who was sentenced to life in prison in 2013.

The Chinese court said it would seize the villa, which prosecutors say was given to Bo and his wife by a businessman friend. One year later, it's unclear if talks have progressed, or even started. The court did not respond to a request for comment.

(1 dollar = 6.1510 Chinese yuan)