The Congolese army on Saturday announced a new operation against armed groups, notably the ADF Ugandan Islamist rebels suspected of murdering 14 UN peacekeepers last month.
Army vehicles transported some 300 troops to the operation's headquarters near Beni in the restive eastern province of North Kivu.
Tanks and armoured vehicles were also deployed, according to an AFP correspondent, who added that heavy and light weapons fire could be heard.
The Democratic Republic of Congo army "has decided to launch an offensive operation against the ADF (Allied Democratic Forces) as well as against armed groups in the Beni and (neighbouring) Lubero areas," army General Marcel Mbangu told reporters.
"For us this is the last time. We are going to fight until we restore peace and security in the regions," he added.
The ADF Ugandan rebel force is one of a number of armed groups acting in North Kivu and South Kivu, the two western provinces which border Uganda, Rwanda, Burundi and Tanzania.
Present in DR Congo since 1995 the ADF opposes Ugandan President Yoweri Museveni's rule.
Congolese authorities and the UN mission in DR Congo, MONUSCO, accuse the group of killing more than 700 civilians as well as combattants in the Beni region since 2014.
The group also stands accused of killing 14 UN peacekeepers in eastern DR Congo last month, the biggest single loss of peacekeepers in nearly a quarter of a century.
On Saturday no UN patrols were visible around the headquarters of the new operation of the Congolese army.
In late December, the Ugandan army announced the launching of air attacks against ADF camps in DR Congo.
Ugandan forces say they have killed around 100 ADF fighters in the operation.