Cambodia will not allow foreign military bases on its soil, premier Hun Sen said 19 November, swatting away US concerns about a possible Chinese naval site near hotly contested seas.

China has lavished billions of dollars in soft loans, infrastructure and investment on the Southeast Asian kingdom, providing Prime Minister Hun Sen with a fast-growing economy.

In exchange Cambodia has been a staunch China ally.

Rumours a Chinese naval base is under construction off Cambodia's southwest coast have been swirling.

The area under scrutiny is in the Gulf of Thailand but gives ready access to the South China Sea.

Beijing claims most of the flashpoint area, infuriating the Philippines, Vietnam, Malaysia and Taiwan who all have competing claims to its islands and potentially resource-rich waters.

But in comments during a cabinet meeting, broadcast on Facebook live, Hun Sen denied military bases of any kind have - or will be - built on Cambodian territory.

‘I have received a letter from Mike Pence, US Vice President, regarding concerns that there will be a China naval base in Cambodia,’ he said.

‘The constitution of Cambodia bans the presence of foreign troops or military bases in its territory... whether naval forces, infantry forces or air forces.’

The US, once the region's undisputed military power, is acutely aware of the strategic and trading importance of the South China Sea and insists it remains international waters.

US, Australian and British warships have increasingly conducted freedom of navigation operations through the sea to press that point, infuriating Beijing.

Hun Sen dismissed reports of a Chinese base as ‘information that only tries to manipulate the truth.’

‘I will reply to the letter from US Vice-president Mike Pence to make him understand clearly about the issue,’ he said, adding ‘we consider all countries as friends.’

Chinese-bankrolled casinos, developments and dams have mushroomed in recent years, fanning growth but incubating resentment among some Cambodians who fear the country is increasingly in the pocket of the regional superpower.

'China and Cambodia are friendly neighbours... co-operation between the two sides is open and transparent,' Chinese foreign ministry spokesman Geng Shuang at a press briefing in Beijing.

'It is not aimed against third parties and cannot be unfairly criticised.'

Several joint military exercises have also taken place while in June Beijing promised $100 million to modernise Cambodia's military.

China has established military positions on disputed outcrops in the South China Sea and intimidates fishermen and naval vessels from rival countries.