Hundreds of people marched in Niger Thursday, demanding the release of two anti-slavery activists jailed for fraud.

The rally was monitored closely by anti-riot police, and no violence was reported.

Two top officials with the anti-slavery group Timidria were arrested several weeks ago on fraud charges. The allegations stem from a planned event in March in which the organization intended to free 7,000 slaves. Organizers say local officials intimidated slaves, preventing them from attending the ceremony.

Niger charged the activists with illegally seeking donor funding for the activity. The government said slavery has been formally banned and does not exist in Niger.

But anti-slavery groups say the practice of inherited servitude persists. They say more than 40,000 people are enslaved in countries bordering the Sahara desert, including Niger.

Some information for this report provided by AP and AFP.