Ugandan troops will spend no more time in the Democratic Republic of Congo helping to fight rebels than "strictly necessary", President Felix Tshisekedi pledged on Monday in an annual address on the state of the nation.

The two neighbors launched artillery and airstrikes on November 30 against the Allied Democratic Forces (ADF), accused of massacres in DR Congo and bombings in Uganda.

The offensive against the deadliest militia in the east of the DRC has seen 34 rebels captured, 31 hostages freed and four enemy camps destroyed, the two armies said on Saturday.

The situation on the ground remained calm since the operations began, their statement said.

"With our parliament duly informed, I will limit these operations, the presence of the Ugandan army on our territory, to the amount of time that is strictly necessary," the president said in the address at parliament.

The speech was the first time Tshisekedi had officially mentioned the presence of Ugandan troops in his country.

After 25 years of violence, he had put the eastern provinces of North Kivu and Ituri under a "state of siege" in May, when soldiers replaced civil servants in key positions.

The president said, "no effort will be spared to restore peace and security".

He noted that the ADF also operates in Uganda and the joint border area and said the state of siege had "moved the lines" and seen former enemy bastions recaptured.

The ADF was historically an Ugandan rebel coalition whose biggest group comprised Muslims opposed to President Yoweri Museveni.

Established in eastern DRC in 1995, the group became the deadliest of scores of outlawed forces in the troubled region where thousands of civilians have died.