U.S. Secretary of State Marco Rubio called for a urgent cease-fire in the conflict in eastern Democratic Republic of Congo saying Washington was "deeply troubled" by a recent escalation in the fighting.

Rwanda-backed rebels captured large parts of eastern Congo’s largest city including its airport, the United Nations said, as Rwanda’s president joined calls for a ceasefire.

GOMA, Democratic Republic of Congo (Reuters) - Rwanda's President Paul Kagame said he agreed with the U.S. government on the need for a ceasefire in eastern Congo but gave no indication of bowing to calls for Rwandan troops and the M23 rebels they support to withdraw from Goma.

Rwanda's ally Uganda, unhappy about another rebel group in DR Congo that threatens its security, has also been accused of helping the M23 - with its officers also spotted at Tchanzu. The UN experts say Uganda has also supplied weapons, hosted rebel leaders and allowed cross-border movements of M23 fighters - accusations Kampala denies.

Congolese rebels and allied Rwandan troops claimed on Monday to have captured the mineral-rich city of Goma, as thousands fled fighting that killed at least 13 peacekeepers over the weekend.