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.

Amid tragic escalation of violence in Congo, Bishop Willy Ngumbi Ngengele of Goma has assured the people of the church's closeness and compassion, as rebels entered the eastern city of Goma, forcing thousands to flee and triggering wave of looting and deaths.

Goma is a lucrative hub because of its niche to valuable deposits of gold, coltan and tin which are minerals essential in the global supply chain for electronics and industrial manufacturing.

Speaking to BBC Newshour while being locked down in a UN bunker in the city, the deputy head of the UN force, Vivian van de Perre, said the M23 rebels had "established" themselves in Goma, but were still facing "pockets of resistance".

Bodies are lying on the streets. Medical staff in overwhelmed hospitals are treating hundreds of wounded civilians against the backdrop of gunfire and explosions. Electricity, water and internet access are cut off,

The M23 rebel group has declared the key city of Goma under its control, signalling a big blow to the Congolese army.

According to reports, the Romanian government and the US intervened to ensure the safe passage of the mercenaries.

The United Nations says Rwanda-backed rebels captured large parts of eastern Congo’s largest city of Goma including its airport. Rwanda’s president meanwhile joined calls for a ceasefire amid mounting