Nguyen Thi Tinh said her husband Nguyen Nang Tinh was seized and pushed into a truck by police officers while he and their two sons were on their way to breakfast May 29, ucanews.com reported.
She said police later asked her father-in-law to get the sons, the oldest of whom is 7, from the police station.
Nang Tinh, 43, had taken the couple's two sons to their home in Vinh City, the capital of Nghe An province in north central Vietnam, from Ho Chi Minh City, where she works.
The official police newspaper in the province said Nang Tinh was arrested for "producing, disseminating or spreading information and documents aimed at undermining" Vietnam.
She said police "have no heart to separate our children from their father." The woman said they had not done anything wrong. She said law enforcement officers should have acted according to laws and their conscience.
Government-supported bloggers reported that Nang Tinh was arrested for joining the Viet Tan pro-democracy group based in the United States. The Vietnamese government considers the group a terrorist organization.
The bloggers said police searched Nang Tinh's home and took materials relating to his "crimes."
Authorities also threatened to arrest other activists, including Father Anthony Dang Huu Nam and Father John Baptist Nguyen Dinh Thuc, whom they described as "reactionaries."
Blogger Paul Tran Minh Nhat said Nang Tinh's family has not been informed about why he was seized.
Nhat said Nang Tinh, who teaches music at a public college of culture and arts in Vinh City, has been involved in human rights, justice, cultural and religious activities at parishes in the Diocese of Vinh and has provided material and spiritual support to victims of social injustice.
After news of the abduction spread, hundreds of Catholics gathered May 29 at My Khanh Church in the province to pray for Nang Tinh.
Presiding at the gathering, Father Nam told the community that "I will be happy if communists hate, persecute, imprison or kill me as they have said because in that way I know I belong to God, the church, the truth and you."
Vietnam holds 128 prisoners of conscience, according to Amnesty International's most recent report.