TAIPEI (REUTERS) - Taiwan on Tuesday (Jan 3) strongly objected to the deportation from Vietnam to China of four Taiwanese nationals suspected of telecommunications fraud, saying the move was carried out under pressure from Beijing.

The latest deportation followed a series of similar cases this year where Taiwanese nationals in Kenya, Malaysia, Armenia and Cambodia have been arrested for alleged involvement in cross-border telecom scam groups and sent to China.

The deportations arose from the "one-China" policy of most countries under which they maintain formal relations only with the People's Republic of China rather than Taiwan, a self-ruled island that Beijing regards as a renegade province.

The four suspects, along with one Chinese national, were arrested in the northern Vietnamese city of Haiphong in December.

Despite repeated requests from Taiwan envoys in Vietnam to have the four deported to Taiwan, they were"forcibly" sent to China, Taiwan's foreign ministry said.

"China said that in this case the victims were mostly in China and demanded Vietnam to repatriate all of the suspects to China (based on a bilateral legal treaty), obstructing our efforts to understand the case and visit the Taiwanese suspects," it said in a statement.

Taiwan's China policymaker, the Mainland Affairs Council (MAC), urged Beijing on Tuesday to open dialogue as soon as possible, saying its actions were unhelpful in tracing the source of the cross-border fraud groups and affected mutual trust in joint Chinese-Taiwanese crime-fighting efforts.

China has suspended dialogue with Taipei since June, a month after pro-independence Thai Ing-wen took office as Taiwan's president, because Tsai has refused to accept Beijing's "one China" principle that deems Taiwan a part of China.

According to MAC officials, there are over 200 Taiwanese suspected of telecom fraud who have been deported from third countries to China this year.

Chinese authorities have sought to contain an explosion of telecom crime it says has led to huge financial losses, with callers often impersonating officials or authority figures and preying on the elderly, students or the unemployed.

The fraud has spread overseas, with Chinese speakers recruited in neighbouring self-ruled Taiwan increasingly setting up operations in East Africa or South-east Asia.