A Hong Kong bookseller who went missing in mainland China and re-emerged under detention returned to his home city Tuesday and asked police to drop their investigation into his initial disappearance.

Lam Wing-kee is one of five Hong Kong-based booksellers who published salacious titles critical of Beijing and disappeared at the end of last year, a case which fuelled growing fears Beijing was tightening its grip on the semi-autonomous Chinese city.

It later emerged that all had been detained in China, where four of them -- including Lam -- are under official investigation over the import of banned books from Hong Kong to the mainland.

Lam is the latest to return to Hong Kong -- three of the other booksellers have also made short trips but have quickly gone back over the border.

Hong Kong police said they met Lam Tuesday morning. Like the others who have come back, he requested the cancellation of his missing person case and said he did not need official help, police said.

Critics have said the retractions were made under pressure from Beijing.

Hong Kong police have said they are continuing to investigate the booksellers' cases.

Lam was one of three who went missing from southern mainland China in October.

Another went missing from Thailand and the fifth, Lee Bo, from Hong Kong.

Lee's disappearance led to accusations that mainland law enforcement agents were operating illegally in the city.

Lam's colleagues Cheung Chi-ping and Lui Por returned to Hong Kong in March on bail, but are reported to have quickly gone back to the mainland. Lam is also on bail.

Lee resurfaced in the city the same month, only to cross back across the border less than 24 hours later. He insists he is a free man and is just assisting mainland authorities.

The men all worked for the Mighty Current publishing house, which produced books about political intrigue and love affairs at the highest levels of Chinese politics.

Bookseller Gui Minhai, a Swedish citizen, confessed to trying to smuggle illegal books into China in a television interview in February.

Lam, Cheung and Lui blamed the company's illegal book trade on Gui.

Hong Kong was returned to China by Britain in 1997 and enjoys far greater liberties than in mainland China, but there are fears these are being eroded.

China economic outlook "uncertain" as vulnerabilities loom: IMF
Beijing (AFP) June 14, 2016 - China's economic outlook is uncertain with corporate debt and an opaque financial sector contributing to looming vulnerabilities, an International Monetary Fund Official said Tuesday.

David Lipton, First Deputy Managing Director at the IMF, said the near-term growth outlook in the world's second largest economy had become more buoyant because of recent policy support but warned of potential pitfalls ahead.

"The medium-term outlook is more uncertain due to rapidly rising credit, structural excess capacity, and the increasingly large, opaque, and interconnected financial sector."

Speaking in Beijing, where he had been meeting senior banking and government officials among others, Lipton said China needed to accelerate the pace of economic reforms as it had fewer options for dealing with future crises.

Corporate debt, state-owned company reform and lack of communication between financial regulators were all cited as vulnerabilities.

He suggested China establish a special group to restructure its hulking state-owned enterprises, which have long suffered from inefficiencies.

Beijing has long vowed to reform the companies, which control critical sectors of the economy ranging from coal production to telecommunications, but institutional resistance has stymied those efforts.

Lipton also singled out corporate borrowing as a major concern.

"Corporate debt, though still manageable, is high and rising fast," Lipton said. "Addressing the corporate debt problem is imperative to avoid serious problems down the road."

Lending obligations in the country have increased dramatically following several rounds of credit loosening intended to stimulate waning growth.

One state-owned company, the China Railway Corporation, owes more than $600 billion in debt, it revealed in May.

Aside from financial concerns, the IMF proposed China institute a carbon tax to clean up the country's heavily polluted skies. If implemented, the IMF predicted the measure could prevent four to five million premature deaths by 2030.

His comments come as China struggles with a tough transition away from dependence on debt-fuelled investment and export industries in an attempt to find a "new normal" of economic growth powered by domestic consumption.

In April, the IMF raised its 2016 growth forecast for China by 0.2 percentage points to 6.5 percent, citing announced stimulus plans. It also increased its estimate for 2017 by the same amount, to 6.2 percent.

The figures still represent a significant drop from the 6.9 percent expansion seen in 2015 -- the slowest in a quarter of a century.