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.

(Reuters) - 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.

Rebels seized the airport of east Congo's largest city, Goma, on Tuesday, potentially cutting off the main route for aid to reach hundreds of thousands of displaced people, after capturing the city in an offensive that left dead bodies lying in the streets.

Much of the beleagured city of Goma was calm early Wednesday morning, after a day during which thousands of fleeing people hunkered down by roadsides as missiles flew and injured people streamed to overwhelmed hospitals.

Congo has severed diplomatic ties with Rwanda as fighting between Rwanda-backed rebels and government forces rages around the key eastern city of Goma.

The United States urged the United Nations Security Council on Tuesday to consider measures to halt an offensive by Rwandan troops and M23 rebel forces in eastern Democratic Republic of Congo as a conflict there escalates.

Rwanda-backed fighters advanced on a second front in their lightning offensive across eastern DR Congo on Wednesday after seizing control of most of the key city of Goma during heavy

Rwanda-backed fighters controlled most of the besieged DR Congo city of Goma on Wednesday as residents slowly emerged from their homes after days of deadly fighting in the key mineral

By Yassin Kombi and Sonia Rolley GOMA, Democratic Republic of Congo (Reuters) - Rwandan-backed rebels strengthened their control over east Congo's largest city, Goma, on Wednesday as columns of Romanian mercenaries hired to fight for Congo entered Rwanda under tight supervision by Rwandan security forces.

Rwanda-backed fighters advanced on a second front in their offensive across eastern DR Congo on Wednesday after seizing control of most of the key city of Goma during heavy fighting with the Congolese military.