Rwandan President Paul Kagame blasted criticism of his country's role in eastern Democratic Republic of Congo where rebels his government backs have seized its largest city, saying Kigali is prepared for "confrontation" if necessary.

Congo's leader has called on young people to enlist in the army to help fight Rwanda-backed rebels attempting to seize more territory in the country's conflict-battered east.

Rwanda, which diplomats say backs M23 fighters who seized Goma in Democratic Republic of Congo this week, called on Wednesday for a ceasefire across eastern Congo and for Congo to negotiate with the rebels while denying Rwandan troops were involved.