By Yassin Kombi and David Lewis GOMA, Democratic Republic of Congo (Reuters) -As an East African bloc urged an immediate ceasefire in eastern Democratic Republic of Congo, Rwandan-backed M23 rebels who seized the city of Goma extended their advance on Wednesday,

Kenya has announced a virtual crisis summit, but Congolese state media says President Felix Tshisekedi will not attend.

M23 rebels, with support from Rwandan troops, are now advancing toward the capital of neighbouring South Kivu province, in the biggest escalation since 2012 of a decades-old conflict

The rebels, which Rwanda denies supporting, have long been funded at least in part by the illicit mineral trade.

Many Congolese see the rebel advance as an invasion of their country by a foreign power in an attempt to seize land and Congo’s valuable rare minerals.

Rwandan backed rebels have entered the city of Goma, a key city in neighboring Democratic Republic of Congo. Could the mineral rich region be in danger of tipping into all out regional conflict?

M23 insurgency in eastern Democratic Republic of Congo has intensified in January with the M23 rebels seizing control of more territory than ever before, prompting the U.N. to warn of the risk of a broader regional war.

A lightning advance in Congo's mineral-rich eastern borderlands is set to boost the M23 rebellion's illegal mining revenues, with analysts predicting a further surge in illicit trade in minerals including coltan and gold through neighbouring Rwanda.

Democratic Republic of Congo President Felix Tshisekedi has insisted that his troops are mounting a "vigorous" response to Rwanda-backed fighters advancing in the country’s perennially troubled east,

Rwandan-backed M23 rebels in Democratic Republic of Congo were moving south on Wednesday towards Bukavu, the capital of South Kivu province, in what appeared to be an attempt to expand their area of control in the country's east after capturing the city of Goma.

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.