Hanoi  - Vietnamese authorities have arrested a US student, who is a member the Democratic Party of Vietnam, while travelling to Vietnam with a nonprofit humanitarian group to do charity work, a party official confirmed Monday.

"This arrest is unlawful," Nguyen Si Binh, chairman of the US-based Democratic Party of Vietnam (DPV), told the German Press Agency dpa by telephone.

The DPV on its website said Vo Tan Huan, 26, a Vietnamese-American member of DPV and a student of pharmacy at the University of Tennessee, traveled to the Asian country with Project Vietnam, US-based a nonprofit humanitarian group, to do charity work at Children's Hospital II and was arrested in Ho Chi Minh City on July 16.

The DPV is calling on the US State Department to request the government of Vietnam immediately intervene and release Huan.

Vietnamese authorities and media have not provided information related to the arrest.

The arrest followed the arrest two pro-democracy campaigners, Nguyen Tien Trung, 26, and Tran Anh Kim, 60, both members of DPV, on July 7 on charges of "acting to undermine the State, violating Article 88 of Vietnam's Criminal Code." (dpa)