Vanuatu has denied bowing to pressure from Beijing by allowing Chinese police to enter the Pacific island nation and extract six criminal suspects without them facing a local court.
Critics have accused the government of bypassing due process to please China, one of the country's biggest aid donors.
It also comes as Beijing vies for influence in the area with traditional regional powers, including the United States, Australia, and New Zealand.
"Under a veil of secrecy, China has convinced Vanuatu to enforce Chinese law within its own borders," wrote the Vanuatu Daily Post newspaper, which broke the story of last week's deportations from the capital, Port Vila.
It said plainclothes police officers from both countries flanked five men and one woman -- all reportedly Chinese nationals -- as they were escorted onto a privately chartered plane last Friday that then flew to China.
Four of the six reportedly had Vanuatu passports obtained under a scheme allowing wealthy foreigners to get citizenship in return for substantial fees or investments.
The situation has been likened to a case in Fiji two years ago when China's uniformed police escorted 77 hooded and handcuffed Chinese nationals who were allegedly part of an online fraud network out of the country.
Internal Affairs Minister Andrew Napuat told Radio New Zealand there was nothing unusual about last week's operation, and said foreign criminals should not obtain citizenship in an attempt to hide from the law.
"To those other foreigners who have obtained Vanuatu passports through the citizenship programme, you must understand that the government can revoke your passports at any time if you are caught in illegal acts," he told the Daily Post.
"We will be strengthening our border compliance and rules."
Port Vila introduced its Economic Citizenship Programme to generate income and bring in wealthy businessmen after the nation was devastated by Cyclone Pam in 2015.
Foreigners can gain Vanuatu passports for fees ranging from $200,000 to $280,000 -- or if they invest $230,000 in the country's real estate.
The International Monetary Fund (IMF) said earlier this year that the scheme -- which supposedly includes criminal background checks on all applicants -- had generated 3.5 billion vatu ($30.4 million) two years ago, or roughly three percent of the country's total gross domestic product.
However, the IMF warned the government needed to end its reliance on revenues from the scheme as they were set to decline in coming years.