Tea Banh said the 12 Chinese-built Zhi-9 army utility helicopters would be for use mainly in humanitarian missions. He did not disclose the cost of the helicopters.

"Clearly, these will help our efficiency and capability," Tea Banh said during a ceremony in which the Deputy Chief of Staff of China's military, General Qi Jianguo, signed an agreement to help train Cambodia's armed forces.

China has played a key role in improving Cambodia's dilapidated military inventory over the past two years, as well as providing big loans and a slew of large-scale investments in construction, energy, transport and agriculture.

That influx of cash has earned China a small but significant ally in Southeast Asia as the United States seeks to boost its footprint in the region to capitalise on its growth and counter Beijing's growing influence.

Critics accuse China of using its economic muscle to ensure Cambodia works in its strategic interests within the 10-member Association of Southeast Asian Nations (ASEAN), which requires consensus on all decisions.

In the past year, Chinese companies have pledged to invest $8 billion in Cambodia, a figure equivalent to almost two-thirds of its entire economy. The $195 million loan was made in late 2012.

The alliance between the two countries expanded to defence support in 2010 when Beijing donated 250 jeeps, trucks and ambulances to Cambodia's army after the US scrapped its plan to provide the military with 200 vehicles.

That was in response to Cambodia sending 20 ethnic minority Uighur asylum seekers back to China in 2009 at Bejing's request.

Much of Cambodia's military equipment is outdated and in need of repair, with only a few helicopters currently in use.