China delivered 600,000 doses of its Sinopharm coronavirus vaccine to ally Cambodia on Sunday, making the kingdom the latest country to use Chinese jabs despite concerns about their efficacy compared to Western alternatives. 

Cambodian leader Hun Sen announced last month that China would donate one million doses of its coronavirus vaccine to the kingdom -- which will cover 500,000 people because two doses are required.

On Sunday, the strongman premier greeted the arrival of the first batch at Phnom Penh's international airport. It's unclear when the remaining doses are scheduled to touch down.

"The Cambodian government owes gratitude to the Chinese government," Hun Sen said during a handover ceremony at the airport. 

Hun Sen, 68, one of the world's longest-serving leaders, originally planned to receive the first shot of the vaccine, but he backed away from that idea after learning it's aimed at people aged between 18-59.

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

Cambodia plans to vaccinate at least 10 million of its 16 million population with shots from both China's Sinopharm and Sinovac as well as the British-Swedish AstraZeneca.

Sinopharm said in December that its vaccine had a 79.34 percent efficacy rate, lower than rival jabs developed in the West by Pfizer-BioNTech and Moderna -- with 95 and 94 percent rates respectively.

Beijing has repeatedly insisted that the jab is safe and effective, despite not releasing any detailed clinical trial data.

Cambodia has long been a staunch ally of Beijing's, receiving billions of dollars in soft loans and investments.

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

Cambodia has weathered the pandemic relatively unscathed, registering only 474 cases with no deaths, though experts say the low numbers are likely due to a lack of testing.