The move showed "contempt for human rights," Taiwan's Mainland Affairs Council (MAC) said in a statement
to Chinese state-run news agency Xinhua, the five Taiwanese were part of a group of 40 fraud suspects brought from Kenya to China in police custody on Monday.
The deportees are accused by Chinese authorities of being involved in dozens of fraud cases worth upwards of $600,000. They were arrested by Kenyan police in November 2014, Xinhua said.
They are part of the same group deported from Kenya to mainland China in April, who were also accused of fraud. That group included 45 Taiwanese citizens, sparking a diplomatic incident between Taipei and Beijing
Many of the suspects deported to China had previously been acquitted by a court in Nairobi of running a complex phone and internet scamming operation, but then later charged by Chinese authorities. Chinese officials said the Taiwanese nationals confessed after being flown to China
At the time, China's Ministry of Foreign Affairs spokesman, Lu Kang, said "the one China policy is an important precondition for bilateral relations with China and other countries. We commend Kenya for implementing this policy."
The "one China" policy is the principle that Taiwan and China are part of the same country. The governments of Taiwan and China both claim sovereignty over mainland China and Taiwan -- but crucially, neither recognizes the other's legitimacy.
Kenya does not recognize Taiwan -- officially the Republic of China (ROC) -- nor does it maintain diplomatic relations with the island. Only a handful of states, mainly small island nations and South American countries, recognize the ROC
According to Xinhua, Chinese police "kept their Taiwan counterparts informed of all developments" with regard to the latest deportations.