By Jonny Hogg and Anna Yukhananov
GOMA, Democratic Republic of Congo (Reuters) - Eastern Congo has the best chance in years to secure a lasting peace but the United Nations stands ready to pacify the region by force if need be, Secretary General Ban Ki-moon said on Thursday.
Fighting that erupted on Monday near Goma, eastern Democratic Republic of Congo's largest city, has killed at least 20 people and ended an uneasy six-month calm between the army and fighters from the M23 rebel group.
"We have the best chance in many years to bring peace, stability and development to this country and this region," Ban said on a visit to Goma with World Bank President Jim Yong Kim.
A day earlier, the bank announced it would provide $1 billion to help finance health and education services, hydro-electric projects and cross-border trade aimed at fostering development and peace in the conflict-ridden Great Lakes region.
Ban has said the money is contingent on countries in the region honoring a peace deal brokered by the United Nations in February to try to end two decades of conflict in eastern Congo.
This week's fighting was the first since November, when M23 troops routed the army and briefly seized Goma, despite the presence of thousands of U.N. peacekeepers.
Ban said a new U.N. Intervention Brigade tasked with neutralizing armed groups across the eastern border region would be deployed within the next month or two to support the existing 17,000-strong U.N. mission.
"This time, we're going beyond the traditional way of peacekeeping missions. (The brigade) has been mandated with a clear and robust mandate to enforce peace when it is necessary," he said.
The first troop contingents for the brigade, which will include some 3,000 soldiers from South Africa, Tanzania and Malawi, have already begun to arrive.
Ban told Reuters that Congo's U.N. mission, MONUSCO, would begin using surveillance drones in August to monitor the border - a thickly forested area of rugged terrain with few roads.
Following three days of heavy weapons exchanges on the outskirts of Goma, the rebels announced a ceasefire hours before Ban and Kim's arrival.
M23 spokesman Amani Kabasha demanded that Congolese President Joseph Kabila also sign a formal ceasefire. "We're very happy that Ban Ki-moon is coming to Congo so he can see that the real problems are deeper than they appear," he said.
M23 is made up of members of a previous Tutsi-dominated rebellion who integrated into the army after a 2009 peace deal.
They deserted en masse last year accusing the government of failing to honor the terms of the deal and have since expanded their demands to include calls for sweeping political reforms.
Talks between M23 and Congo's government, which had been taking place in Uganda, have stalled.
U.N. experts have accused Rwanda, one of 11 African nations that signed the regional peace deal in February, of sending troops and weapons across the border to support the M23 last year. Rwanda denies the accusation.
Ban said he would push President Paul Kagame to stick to the terms of the U.N.-brokered peace deal when he travels to Rwanda on the next leg of his three-country trip on Thursday.
"I believe that he has to show there's a strong commitment to keeping this (peace agreement)," he told Reuters. "He said to me that he's very strongly committed to full implementation of this framework agreement. That is why I am going there."
The International Committee of the Red Cross said 15 people, including five children, were wounded on Tuesday and Wednesday when shells fell on a densely inhabited Goma neighborhood and around a nearby camp for civilians displaced by war.
The Human Rights Watch group said on Wednesday that a 2-year-old girl had been killed by one of the shells, which the United Nations later said had been fired from M23 positions.
"Thousands of people live in the neighborhoods located close to the fighting," said Rachel Bernhard, head of the ICRC's delegation in Goma. "These residents and displaced people are once again caught in the crossfire, their lives at risk."
(Writing by Joe Bavier; Editing by Daniel Flynn and Robin Pomeroy)