From a windowless room in a dilapidated Hong Kong high-rise, Ali Diallo sells Chinese electronics to retailers across Africa. The modest surroundings belie the multi-million dollar business the West African trader has built in the five years since he moved to the city.

The 39-year-old from Guinea is part of a growing number of African entrepreneurs thriving in southern China, as trade between the world's second-largest economy and fastest-growing continent soars.

Sitting in a small room cluttered with cardboard boxes destined for Nigeria, Diallo welcomes the latest delivery of Chinese-made mobile phones to his office in Chungking Mansions -- a bustling labyrinth better known for budget hotels and no-frills restaurants.

The building is also the go-to place in Hong Kong for African buyers in search of cheap electronics, with phones selling from around $8 each.

"In China there are opportunities for people who can start from scratch and build up their own business. Obviously not in one day but through hard work and networking you can do it," says the trader, whose company sees an annual turnover of $11 million a year through the sale of phones and tablets alone.

Trade between China and Africa hit new highs of nearly $200 billion last year, according to official Chinese data, driven by Chinese industry's appetite for African raw materials.

The African traders in southern China are the flipside of this deepening relationship. Entrepreneurs like Diallo have made Chungking Mansions one of the most important passageways for Chinese gadgets air-freighted to Africa.

According to Gordon Mathews, professor of anthropology at the Chinese University of Hong Kong, up to a fifth of all mobiles in Africa have passed through the building's corridors in recent years.

But while this 17-storey hive is the storefront, the engines behind this trade lie in the industrial heartland of neighbouring Guangdong province in southern China.

This mecca for low-cost manufacturing has drawn entrepreneurs from across Africa, creating one of the largest black communities in Asia.

A pivotal role

In the provincial capital Guangzhou, at least 20,000 Africans live in the city, research from local Sun Yat-sen University shows.

Though their number is a fraction of the million Chinese now living in Africa, these migrants are playing a pivotal role in their new home.

"Traders bring with them vast skills and capital, supporting large amounts of Chinese manufacturers... If all the African traders were to vanish it would have an enormous effect on the south China economy and business people realise this rather strongly," says Mathews.

Many traders work in and around a downtown neighbourhood dubbed "Little Africa", or more insensitively "Chocolate City" by the local media. Along its winding central alley, a restaurant serves Tilapia with fufu -- a staple Congolese meal of fried fish and cassava -- as well as traditional Chinese fried rice and steamed fish.

A few kilometres away at Canaan Export Clothes Trading Centre, a vast complex where Igbo is spoken as often as the local Cantonese language, Lamine Ibrahim loads thousands of jeans into bags destined for Africa.

He is one of several hundred Africans who has forged a deeper connection to the city by marrying a local Chinese woman -- a relationship founded on love but also economic prudence.

"For (communication) with the Chinese people... she can do. I buy my car, she is there, I open my own factory, she is there. So if I have no wife it's not easy," says the Muslim trader from Guinea in broken English.

Five months ago Ibrahim and his wife Choi Zoung-mai -- renamed Maryam Barry after converting to Islam -- opened their first factory hiring 43 Chinese workers. With this latest investment they hope to secure a bright future for their four-year-old son who speaks fluent Mandarin as well as French, English and Fula.

Prejudices can run high

While there are several success stories, not all African entrepreneurs make it in China -- for some rising costs and intense competition make it difficult to stay afloat. But this migrant community, which began forming in Guangzhou in the 1990s, has built a network of groups to support each other's ambitions.

This is vividly apparent in the handful of African Pentecostal churches that have sprung up across the city. Tucked away on the ninth floor of a building behind Guangzhou railway station, 150 worshippers crowd into Royal Victory Church.

"Our prayer is that you will prosper," the pastor preaches to cries of agreement from a mostly male congregation drawn from Nigeria, Cameroon and Ghana.

The African entrepreneurs who are flourishing in Guangzhou are succeeding where many foreigners fail. Not only are they navigating the notorious Chinese bureaucracy but at times overt racism in a country where prejudices can run high.

This can range from mild snubs from taxi drivers who refuse to pick up black customers to more serious accusations of traders being unfairly targeted by police when they conduct raids for illegal immigrants.

Even so others report good relations with the Chinese. "Many traders feel much more comfortable working in China than they do in Europe," says Roberto Castillo, a Lingnan University researcher in Guangzhou.

Ojukwu Emma, president of the local Nigerian community, says the main problem for Africans trading in China are the increasing clampdowns on visas. He says it is getting harder for African residents in the city to renew visas, or for those travelling back and forth to gain re-entry.

"You cannot allow foreigners to come in and not give the foreigner confidence to stay. Once you are out to the world, you must be open," says the businessman who has lived in the city for 16 years.

But for now booming Sino-African trade continues to draw new waves of African entrepreneurs, drawn to the shores of Guangzhou in search of the Chinese dream.