Dung, 58, is accused of taking bribes and police have searched his house, the ministry said in a statement.

Dung's arrest is part of a wider investigation where foreign ministry officials have been accused of taking bribes from Vietnamese citizens abroad who have wanted to return to the country on "rescue flights" at a time during the COVID-19 pandemic when commercial flights were not available, according to state media.

Dung was appointed Vietnam's ambassador to Japan in January but hadn't officially taken the post.

The Ministry of Foreign Affairs didn't immediately respond to a Reuters request for comment.

The police on Thursday also arrested an official of the Health Ministry and an official of the Ministry of Public Security for involvement in the same case. Four foreign ministry officials were arrested earlier in January.