In sub-zero winter cold, trainees at an army base outside Beijing wake before dawn to practise martial arts and evasive driving, while a Portuguese ex-special forces soldier barks commands.

"We are not polite any more... we are only efficient," declares Marco Borges -- his words rapidly translated into Chinese -- before slapping several of his charges in the face, to giggles from the other students.

But despite their dark uniforms and heavy black boots these are not the latest recruits to some new unit of China's People's Liberation Army.

Instead the roughly 40-strong group -- mostly with previous military experience -- are on a commercial training course to become elite bodyguards protecting Chinese firms as they seek ever more resources and contracts in some of the world's most unstable regions.

The best will be recruited by the school's sister company Genghis Security Advisor (GSA), which offers protection for China's wealthiest citizens from attacks and kidnapping at home and abroad -- a service analysts say could push the government in Beijing into unwanted foreign entanglements.

"Our main jobs will be abroad, because, as our teacher taught us, the situation there is much more unstable than in China," said Li Qinsi, a 29-year-old trainee sitting on a dormitory bunk after an intense fighting class.

Chinese citizens have been targeted by hostage-takers in countries as far-flung as Pakistan, Nigeria and Indonesia in recent years, with the latest incident in Sudan last weekend, and Chinese resource firms have a growing presence in Afghanistan.

"There are lots of rich people in China who have businesses in Europe, in Africa, everywhere" said Borges, an imposing presence in his black uniform and beret. "They are what we would call, in professional language, soft targets."

GSA's founder Chen Yongqing is a former member of the PLA and learnt bodyguard techniques in Israel, a world leader in the field. The firm has permission to use part of the army base but no other connections with the government, he says.

"The bodyguard market in China is huge, but no one is serving it," Chen said. "Lots of Chinese businesspeople have been injured abroad, but it shouldn't be a problem for our company to protect them."

The three-week basic bodyguard course costs 28,600 yuan ($4,600), and those who pass can be flown to Israel for advanced weapons training, Chen said.

The school is known for its tough regime, sometimes carried out in snowy fields or the strength-sapping heat of tropical beaches.

"The situations our bodyguards could face in Israel, or Libya, will be more harsh than they can imagine, so they need to experience that harshness during training," Chen said.

At the base trainees stooped to hoist classmates onto their shoulders before bundling them into the back of a van, to simulate rescuing a client.

GSA declined to specify how many bodyguards it had trained, but said it had sent personnel to the US, Europe and South America, and the school's graduates can also be recruited by other firms looking to protect Chinese interests overseas.

Chinese security contractors were involved in rescuing 29 of their compatriots kidnapped by Sudanese rebels last February, the Wall Street Journal reported, citing Sudanese army sources.

A senior foreign affairs advisor for China's government said last year that Chinese security companies should be "allowed to head abroad".

Han Fangming told the 21st Century Business Herald that China should "seriously discuss" creating an equivalent to America's Blackwater security firm "to provide armed security for overseas institutions and enterprises in high-risk areas".

But the activities of Blackwater -- now known as Academi after two name changes -- have been hugely controversial, with some of its staff accused of killing civilians in Iraq and Afghanistan.

Analysts say Beijing -- which has a long-stated policy of non-intervention in foreign conflicts -- could become embroiled in situations involving China's private security firms.

Armed Chinese contractors, especially in areas such as Africa, will "eventually" engage in firefights, said Gabe Collins, founder of independent Chinese Research website China Signpost.

Beijing could come under pressure to launch "some kind of military operation to rescue contractors that got into trouble," he said.

Even so, 22-year-old Wang Wenwen, one of several women training at the academy, has no doubts about her choice of profession.

"The training is torture, but I can still take it," she said.

"Women have certain advantages... your opponent will overlook you, and you can grab a pen from a desk and stab it here," she said, pointing at her neck. "It has a high rate of success"