The clash between Han Chinese and Uighur workers on June 25 at the Xuri factory in the southern province of Guangdong left 118 injured, 14 of them seriously, state media reported.

Chinese officials, Uighur exiles and rights groups have all said the killings were a trigger for protests thousands of kilometres away in Xinjiang's regional capital Urumqi on Sunday.

The protests spilled into deadly violence that left more than 150 dead, some of the worst ethnic unrest in China in decades.

The original Guangdong incident was sparked by an Internet rumour posted by a disgruntled former worker alleging that six factory workers from Xinjiang had raped two girls, according to China's official Xinhua news agency.

The factory, which is owned by one of Hong Kong's richest men, Francis Choi, had recruited 800 migrant workers from Xinjiang over the previous two months, Xinhua reported, part of a huge influx of workers to coastal cities.

Guangdong authorities moved quickly to try to dampen tensions.

The man who made the Internet posting was arrested, official reports insisted no rape had taken place and Guangdong?s communist party chief, Wang Yang, met relatives of the dead to offer his condolences, Xinhua said.

Wang, who is often seen as a future leader of China, promised no effort would be spared to hunt down the killers.

"We should not allow such an occasional case to affect economic cooperation between east and west zones or our national unity," Wang added, according to the South China Morning Post.

Amnesty International said the authorities also told websites and discussion boards to delete any posts related to the attack.

Despite the efforts, some Uighurs were not satisfied.

The Uighur American Association put out a statement saying unconfirmed reports indicated that more people had been killed in the attack.

It also said unverified reports suggested "local security forces did not take an active role in stopping the violence."

Nur Bekri, chairman of the Xinjiang region, explicitly linked the statement with Sunday's deadly violence.

"After the (Guangdong toy factory) incident, the forces abroad hyped it up greatly," he said, adding that Internet postings had further fomented anger.

On Tuesday, Xinhua reported that police had detained 15 suspects with links to the factory brawl, an apparent additional effort to calm tensions.

Xinhua said earlier this year 1.4 million migrant workers had left Xinjiang in 2007 to look for work in the richer eastern cities, a steep rise from five years ago.

The policy to encourage such migration was meant to be a win-win for workers, authorities and manufacturers.

The factories would be supplied with cheap labour and the workers would be able to send money back to some of the poorest areas of China.

For Xinjiang authorities, worried about Uighurs struggling to find work, it also helped to disperse a large group of angry young men.

But Li Qiang, executive director of New York-based China Labor Watch, said poor conditions at many factories and a lack of integration had instead fuelled tensions.

"This migration has led to countless problems," Li told AFP.

"Because factories tend to see labour as a short-term, replaceable commodity, they largely opt to not invest in training or language classes that may help Uighur people adjust to the new environment."

The case also shines a light on the huge, anonymous Chinese factories that produce much of the world's toys, clothes and electronics.

Early Light Industrial, the Hong Kong company that runs the Xuri factory, has in the past supplied toys for US giants Mattel and Hasbro. It has as many as 20,000 workers at its factories in Guangdong.

Manufacturers have been under huge pressure in the past two years after decades of staggering growth.

Tougher labour and environmental laws and the collapse in demand for goods over the past 12 months because of the global financial crisis have all pummeled the low-margin, high-volume manufacturers, leading to mass closures.

Early Light Industrial declined to comment to AFP about the original killings and the latest violence.