Cambodia will deport 21 Taiwan residents to the Chinese mainland, a senior Cambodian official said on Monday.

Taiwan officials were seeking to have them returned to the island, but Cambodia does not have official relations with Taiwan as it acknowledges the island to be part of one China.

Cambodia detained the 21 Taiwan residents along with 14 Chinese mainlanders in coordination with Chinese authorities, which are attempting to halt the proliferation of internet and phone extortion scams that have cost billions of dollars and driven some victims to suicide.

Uk Heisela, chief investigator of Cambodia's immigration department, said "they have all confessed to committing the crime", and Cambodia will deport them to the Chinese mainland under the one-China policy.

A date for their deportation has not been set yet.

Taiwan officials based in Vietnam traveled to Cambodia but were not allowed to visit the suspects from the island, according to Taiwan authorities.

However, Heisela and Kem Sarin, spokesman for Cambodia's immigration department, said they were unaware of a visit by the Taiwan officials.

Cambodia has deported more than 200 people suspected of involvement in telephone scams to the Chinese mainland since November.

In all, nearly 8,000 people have been arrested since 2011 in countries including Indonesia, Cambodia and the Philippines on suspicion of involvement in similar fraud schemes.