“No authority has confirmed their involvement, but we believe the intelligence services were behind the kidnapping,” he said.
Intelligence services in Mali don't speak with the media about such cases, and other government authorities weren't immediately available to comment.
Abba, who was the secretary-general of the Codem party, was seized and taken away on May 9 shortly after he spoke out against the crackdown on civic rights in the country and the ruling junta's failure to hold an election since a coup in 2021.
His arrest came amid pro-democracy demonstrations in Bamako that criticized the growing dictatorship under the junta and called for the return of democracy. Several political figures are still detained after criticizing the military government's power.
Mali, a landlocked nation in the semiarid region of Sahel, has been embroiled in political and security instability that swept across West and Central Africa over the last decade.
The nation has seen two military coups since 2020 as an insurgency by jihadi groups linked to al-Qaida and the Islamic State group worsened. Arrests of pro-democracy activists have multiplied in response to demonstrations.
In May, Gen. Assimi Goita, president of the country's transitional government, signed a decree dissolving political parties following a demonstration by several hundred pro-democracy activists.