The M23 rebel group has seized the town of Kalembe in eastern Democratic Republic of Congo, expanding its reach in the region, an official and a former lawmaker said on Monday.

The Tutsi-led M23 has been waging an insurgency in the central African country's violence-torn east since 2022. Congo and the United Nations accuse neighbouring Rwanda of backing the group with its own troops and weapons. Rwanda denies this but says it has taken so-called defensive measures.

Rebels had been stationed 10km from Kalembe for nearly eight months before they seized control of the town on Sunday morning from the Congolese armed forces and the Wazalendo alliance of armed groups loyal to the government, Kabaki Alimasi, an official from Walikale territory where Kalembe is located, told Reuters.

While fighting did not target the local civilian population, many felt unsafe and moved to the town of Pinga in Walikale after the attack, the local official added.

The Congolese army did not immediately respond to a request for comment.

Former lawmaker and Walikale resident Juvenal Munobo also said Kalembe had fallen under M23 control and told Reuters that the rebels were interested in the area's gold mines.

The majority of Congo's substantial mineral wealth is found in its eastern provinces. M23 has been making hundreds of thousands of dollars a month from minerals smuggled illegally from territory it has seized, the United Nations said in September.

"We believe that the M23 also want to turn up the heat in anticipation of the upcoming exchanges," Munobo said, referring to negotiations between Congo and Rwanda in the Angolan capital Luanda which are part of a long-running effort to curb the fighting.

The conflict has deepened a humanitarian crisis in militia-plagued North Kivu province, where around 2.6-million people were displaced as of end-September, according to the UN aid agency OCHA.