China will donate one million doses of its Sinovac coronavirus vaccine to Cambodia, the kingdom's strongman premier Hun Sen has said, thanking "friend" Beijing for its generosity.

Cambodia has long been a staunch ally of Beijing, receiving billions of dollars in soft loans and investment from China.

While many countries reacted early in the pandemic by closing its borders to Chinese travellers, Hun Sen refused, and even travelled to Beijing to meet with leader Xi Jinping in a show of solidarity.

The premier announced late Friday that China has offered to donate shots made by the firm Sinovac.

"Friend China is helping us with one million doses," Hun Sun said in an audio message on his official Facebook page, adding that the doses will vaccinate 500,000 people.

"To prevent the nation and people from being infected with this deadly virus, we have to use vaccines that were already used on Chinese leaders and millions of people... We cannot wait any longer."

The first people to get the jab would include frontline health workers, teachers, soldiers, the premier's bodyguards, and officials around the king, he said.

Sinovac's CoronaVac was rolled out in Turkey on Friday, after tests there showed it to be 91.25 percent effective.

But more robust trials in Brazil demonstrated an efficacy rate of around 50 percent -- much lower than those of rival shots from Moderna, Pfizer-BioNTech and Oxford-AstraZeneca.

A third trial in Indonesia -- where authorities this week kicked off a mass vaccination drive with CoronaVac shots -- showed an efficacy of 65.3 percent.

Cambodia has appeared to do well in the pandemic so far, registering just 436 cases, though experts say the low numbers are likely due to a lack of testing.

Beijing has also offered to help another nation in the region, with Chinese Foreign Minister Wang Yi promising this week to provide 300,000 doses to Myanmar.