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GOMA, Congo (AP) — Rwanda accused neighboring Congo of escalating tensions between the two countries on Sunday, a day after the Rwandan ambassador to Congo was given 48 hours to leave the country following rebel advances in the east.

Congo believes that Rwanda is supporting the M23 rebels, who have expanded their control over the past year. On Saturday, residents said the rebels gained control of two more towns, including Kiwanja.

In a statement issued after Rwandan Ambassador Vincent Karega was order to leave Congo, the Rwandan government said its forces along the border “remain on alert.”

“It is regrettable the government of the DRC continues to scapegoat Rwanda to cover up and distract from their own governance and security failures,” said the statement attributed to the Office of the Government Spokesperson.

In a sign of mounting tensions, about 100 demonstrators in Congo marched through the streets of Goma from the city center to the Rwandan border, denouncing “Rwandan aggression.” Some carried torn Rwandan flags and chanted hostile slogans. At the border, a Rwandan flag was set on fire.

The M23 rose to prominence more than a decade ago when its fighters seized Goma, the largest city in Congo’s east, which sits along the border with Rwanda. After a peace deal, many of M23′s fighters were integrated into the national military.

Then the group re-emerged last November, saying the government had failed to live up to its decade-long promises. By June, they had seized the strategic town of Bunagana near the border with Uganda.

M23 has been a flashpoint for relations between Congo and Rwanda: Many of the M23 fighters are Congolese ethnic Tutsis and Rwanda’s president is of Rwandan Tutsi descent.

In August, a report by U.N. experts said they had “solid evidence” that members of Rwanda’s armed forces were conducting operations in eastern Congo in support of the M23 rebel group.

Rwanda, though, has repeatedly denied the allegations and has accused Congolese forces of injuring several civilians in crossborder shelling.