By Adam Jourdan and Jackie Cai

SHANGHAI (Reuters) - At the end of Philippines President Rodrigo Duterte's landmark visit to China last month, he held a brief private meeting with a businessman who may have played a crucial role in improving ties between the two nations.

Huang Rulun, a rags-to-riches Chinese billionaire funding two huge drug rehabilitation centers in the Philippines, has been held up by Duterte as a symbol of the relationship between the two nations.

Born to a poor family in coastal Fujian province, Huang was a small-time businessman in the Philippines in the 1980s. He spent five years in Manila's Chinatown district, Binondo, before returning home to found a construction company, Century Golden Resources Group, according to the company's web site.

Huang has a "strong emotional connection" with the Philippines, the company said.

According to its web site, privately-held Century Golden now employs 20,000 people and posted close to $5 billion turnover last year. It owns 20 five-star hotels and 10 shopping malls, including the major Century City complex in Beijing.

Huang maintains a relatively low profile in Beijing, although he has extensive political contacts in his home province of Fujian, said a source who knows the businessman well.

He seems to have hit it off with the Philippines president. After a meeting with Huang, Duterte said that being able to meet him made his October visit to China "more complete," according to a statement from Century Golden.

Duterte also said the Philippines "needs friends like Huang", the company said.

The meeting took place at the Grand Hyatt Hotel in Beijing the day after Duterte declared a "separation" from the United States and a realignment of his nation's foreign policy towards China. He has since back-tracked, and said he was merely pursuing a more independent foreign policy by strengthening ties with China.

For the Philippines leader, Huang's support for the rehabilitation centers is in sharp contrast to the criticism of Duterte's drugs war by the United States and other Western nations.

China, Duterte said, had offered help "without boasting, without news, without publicity".

"This is how you treat your friends," he said in a speech. "You do not go about reprimanding."

At least 2,300 people, mostly small time addicts and peddlers, have been killed in the Philippines since Duterte took office four months ago and started the crackdown.

CLEAN LIVING

About 700,000 addicts have registered with Philippine authorities but the country has few facilities to treat them.

Huang has said he will fund two 10,000-bed rehabilitation centers for drug addicts.

"Drugs have always been a public hazard worldwide," he said in comments emailed to Reuters by a company official. "They hurt people's bodies and disrupt social order."

It is unclear how much he is spending on the centers, whether he will pay for all recurring costs or just the cost of building them, or whether he will receive anything from Manila in return.

Huang declined to be interviewed for this story but has portrayed himself to Chinese media as a clean-living philanthropist and says he is funding the centers to improve ties between the two countries.

"As long as the Philippine government maintains a friendly relationship with China, I am very happy to invest in the Philippines," Huang was quoted as saying by China's state-run Global Times newspaper in October.

"I don't gamble, I don't whore and I don't do drugs," he told the official Securities Daily newspaper in 2013. "Me and my son together can't spend away all my money through our lives. So why not use it to do something meaningful."

Huang, a school drop-out, was a small-time trader in Manila and made "a modest fortune", according to The Philippine Star newspaper. It was not clear what he traded. According to Forbes magazine, he is now worth about $3.6 billion.

Century Golden was one of 17 firms and individuals who made payments to Bai Enpei, the former Communist Party boss of southwestern Yunnan province, in return for favors, according to online court documents from a major corruption case in China earlier this year.

It was not immediately clear if Century Golden faces any further legal proceedings. Huang himself was not named.

Court officials declined comment. Officials at Century Golden also declined to comment on the case.

Huang has been among China's top six philanthropists named by the Hurun Report since it began publishing a list of top donors in 2012, and donated an estimated $125 million in 2015. According to Hurun, the money was donated to education, infrastructure and social welfare projects.

Prior to the Beijing meeting, Huang has seen Duterte three times in recent months to discuss what he could do in the Philippines, according to government officials.

Philippines Health Secretary Paulyn Jean Rosell-Ubial said Huang came up with the idea for funding the rehabilitation centers after meeting Duterte at the presidential palace in July.

"He seems very simple and unassuming. He is mild mannered and seem very kind. He is sincere in helping the Philippines," Ubial told Reuters.

($1 = 6.7392 Chinese yuan renminbi)

(Reporting by Jackie Cai and Adam Jourdan in SHANGHAI, Karen Lema in MANILA and Benjamin Kang Lim in BEIJING; Editing by Raju Gopalakrishnan)