Congolese soldiers on the march near the Ugandan border.
African leaders and international envoys are appealing to Congo's government and M23 rebels to stop fighting.
While a U.N. official says a peace accord is "on the table" -- there were few signs of peace near the Ugandan border.
A rapid Congolese army advance in recent weeks has cornered M23 rebels in the steep, forested hills near the border with Uganda.
On Sunday, M23 announced a ceasefire - a declaration the Congolese army described as a lie.
An M23 political leader complained that the army attacked its positions with heavy weapons. He told Reuters, "We're only fighting to defend our position. That's the logic of war."