The "guidelines for joint operations" set down procedures for enabling operations by the UN mission MONUSCO and the FARDC, as the Congolese army is known, they said.

The accord was signed at Congolese army headquarters on Tuesday by the country's armed forces chief of staff, General Celestin Mbala, and the commander of the UN forces in DR Congo, Affonso Da Costa, according to an AFP reporter.

It fills a long-standing void for "a coordination mechanism at the operational level", Da Costa said.

The agreement coincides with a crackdown by Congolese and Ugandan troops on the bloodiest of the estimated 122 armed groups in the region.

MONUSCO is one of the biggest and costliest UN peacekeeping operations, with around 16,000 military and police and an annual budget of more than $1 billion.

But it has drawn criticism over its effectiveness in the fight against armed groups that plague the country's east, especially the Allied Democratic Forces (ADF).

Linked by the United States to the Islamic State, the ADF has been blamed for thousands of deaths in the Beni area and for recent blasts in the Ugandan capital Kampala.

Mbala said the new guidelines should enable more of the MONUSCO forces to take on a combat role, rather than be restricted to an observer role under the UN's rules of engagement.

Da Costa said MONUSCO "will go from words to deeds".

The force could commit artillery and combat helicopter support for MONUSCO-FARDC operations, he said.

On November 30, Ugandan forces launched strikes on ADF positions in a joint operation with the DRC, and followed this up by deploying troops on the Congolese side of the border.

MONUSCO will not take part in those bilateral operations but the three forces will share intelligence to avoid "friendly fire" casualties.

Meanwhile, the two countries' defence ministers met in Bunia in Ituri province on Wednesday to discuss "harmonising military operations in the framework of pooling forces," the FARDC's regional spokesman, Lieutenant Jules Ngongo, said.

Uganda's minister, Vincent Bamulangaki, told reporters, "We are here as brothers... facing the same enemy."

Uganda's intervention has come despite a crackdown on the ADF by the Congolese armed forces, launched two years ago.

Their joint operation is controversial in a country where many recall the role of Uganda and Rwanda in stoking past instability in the east of the country.