"President [Felix] Tshisekedi has already raised the option of allowing Ugandan troops to enter Congolese territory to chase ADF terrorists together with" UN troops, a presidential adviser told AFP on condition of anonymity.

"But Ugandan troops will not cross the border tonight or tomorrow. All procedures must first be respected, especially with respect to parliament and the DR Congo military command."

A European diplomatic source confirmed the information, telling AFP "We have been informed via our regular channels that President Tshisekedi has authorised Ugandan troops to cross the border to fight the ADF."

The Allied Democratic Forces (ADF) is the deadliest of scores of armed groups operating in the mineral-rich eastern DR Congo that has been blamed for scored of attacks.

The United States has formally linked it to the Islamic State (IS) group.

The ADF began in the 1990s as coalition of armed Ugandan groups, the biggest of which comprised Muslims, who opposed Ugandan President Yoweri Museveni.

It moved into eastern DRC in 1995, establishing itself in the Rwenzori Mountains in North Kivu.

In April 2019, IS began to claim some ADF attacks on social media, presenting the group as its regional branch.