(CNN)When Eugene Ndereyimana woke up last week, he didn't tell his wife where he was going, and she didn't ask. The less she knew, the better, she thought.
The 29-year-old father of two was traveling from his home in Rwanda's southeastern Ngoma district to the northeastern town of Nyagatare for a political meeting on July 15.
But the people waiting for Ndereyimana to arrive lost contact with him when he was just five kilometers (3.1 miles) from the venue.
He hasn't been seen or heard from since.
Ndereyimana is a representative for the FDU-Inkingi, an unregistered coalition of opposition parties against President Paul Kagame, who has been in power since 2000.
He is one of at least five FDU members who have gone missing under mysterious circumstances over the last few years in Kagame's Rwanda.
Opposition politicians and supporting party members say they face intimidation, violence, jail time or the prospect of disappearing for opposing the President and his ruling party, the Rwandan Patriotic Front (RPF). The Office of the President and the RPF have not responded to CNN's request for comment regarding these allegations.
For Ndereyimana, that intimidation began last September, when he was arbitrarily detained by military officers at a local police station, his wife Joseline Mwiseneza told CNN, speaking through an FDU spokesperson.
"For them he was an enemy," Mwiseneza said, referring to the local authorities. She added that Ndereyimana's political activities created difficulties in his everyday life -- from harassment by security forces to the inability to get credit from the local bank.
Rwanda's Investigation Bureau and Rwanda's National Police have not responded to CNN's requests for comment.
Now, Mwiseneza says she doesn't know what to say to their children, who keep on asking where their father is, and fears for her husband's life.
As she waits for answers, others politically aligned with her husband have met violent ends.
In a harrowing case in March, 30-year-old Anselme Mutuyimana, a close aide to FDU president Victoire Ingabire, was found dead in a forest in the country's northwest region.
Residents who found Mutuyimana said he appeared to have died by strangulation, according to the party.