Democratic Republic of Congo President Joseph Kabila on Saturday vowed that defence would be a top priority for his government after the recent brief rebel takeover of a key city in the country's volatile east.

"From now on, our priority will be defending the homeland," Kabila told parliament in his annual address to the nation.

"Defence, nothing but defence, with a dissuasive, apolitical and professional army.

"I call on our youth to massively enlist," he said, adding that "any new attempt at aggression will be suicidal."

Kabila also accused neighbouring Rwanda of backing the push by the M23 rebels, echoing accusations by the United Nations that Rwanda has denied.

"An unjust war has been imposed on us one more time. Everything has already been said about this war of aggression by Rwanda," he said to whistles and cheers from lawmakers.

He also called for a change in the mandate of UN peacekeepers in the country, saying their performance in the crisis was "mixed".

The M23 rebellion, launched earlier this year by army mutineers largely from the ethnic Tutsi community, conquered large swathes of the mineral-rich eastern DR Congo, including its main city of Goma on November 20, before withdrawing following a regional diplomatic initiative.

Their lightening advance had raised fears of a wider war and a major humanitarian crisis in the region, the cradle of two back-to-back wars that shook the area from 1996 to 2003.

The M23 rebels and government delegates are currently locked in negotiations in Uganda trying to hammer out an agenda for peace talks.

Uganda has also been accused by the UN of backing the rebels. Like Rwanda, it denies the charges.