Suspected Allied Democratic Forces (ADF) rebels freed more than 1,300 prisoners in an assault on a jail in Beni, eastern Democratic Republic Congo.

Only about 100 prisoners after the attack on Kagbayi prison on Tuesday morning.

The ADF are a Ugandan rebel group with bases in eastern Congo.

"We had a count before the escape of 1,456 (prisoners), 110 (of them) stayed and I thank them for that. Some 20 (escapees) have already returned and I know that others are on their way back. We'll do a tally, and work out how many have come back", said Modeste Bakwanamaha, the mayor of Beni.

Kagbayi prison is used to hold errant army soldiers and militiamen captured in fighting, including some from the ADF.

Prison breaks are common in Congo where conditions in detention facilities are said to be very bad.