Fighting between government forces and M23 rebels resumed Tuesday around the strategic town of Sake in eastern Democratic Republic of Congo, sources said.

Clashes have intensified in recent days around the town, which lies about 20 kilometres from Goma, capital of the North Kivu province.

Residents of Sake told AFP by telephone that the battle was taking place on the hills overlooking the area.

"Despite the situation, we control the town of Sake," a security source said, after heavy clashes on Monday.

"Fighting is under way at this moment," the source added.

The town’s "chief", or mayor, Maombi Mubiri said the population had fled.

"For now, the rebels occupy the southern part," of Sake, "the wazalendo (pro-government militia) are in the northern part," the mayor said.

A medical source said sporadic fire could be heard and three wounded people had been treated and transferred to Goma.

"The town has not been taken by the rebels yet," the source added, asking to remain anonymous.

The mostly-Tutsi M23 group has seized vast swathes of North Kivu since emerging from dormancy in late 2021, in a region ravaged by violence for decades following regional wars in the 1990s.

Congolese Defence Minister Jean-Pierre Bemba, on his second visit to Goma in less than a week, offered reassurances that "everything is being done to protect the people of Sake, Goma and the surrounds".

Kinshasa intends to "retake all the territories" lost to the rebels, said the minister.

The United Nations Security Council on Monday voiced concern at "escalating violence" in eastern DRC and condemned the rebel offensive launched near Goma on February 7.

According to a UN document seen by AFP, the Rwandan army is using sophisticated weapons such as surface-to-air missiles to support M23.

A "suspected Rwandan Defence Force (RDF) mobile surface-to-air missile (SAM)" was fired at a UN observation drone last Wednesday without hitting it, the confidential report said.

Tensions are running high between Kinshasa and Kigali.

The DRC, the UN and western countries say Rwanda is supporting the rebels in a bid to control vast mineral resources, an allegation Kigali denies.

M23 says it is defending a threatened minority and seeks negotiations with the government, which refuses to talk to what it calls "terrorists".

A flurry of diplomatic efforts to halt the fighting has so far failed to find a lasting solution.

On Tuesday, Burundi announced that President Evariste Ndayishimiye would visit DRC "in the framework of consultations" for a regional peace agreement.