( CNN ) -- Tension loomed in the Democratic Republic of the Congo city of Goma on Monday night as rebel commanders refused to leave the city ahead of a midnight deadline imposed by regional leaders and the African Union . African leaders convened in neighboring Uganda over the weekend and released a statement demanding that the M23 group withdraw at least 20 kilometers ( 12 miles ) north of Goma as a condition of initiating negotiations . The leaders called on the rebels to `` stop all war activities , '' and `` stop talk of overthrowing an elected government . '' But M23 leaders said Monday that they will leave the conflict-scarred city only if talks are successful . Both rebel and government troops were massing west of Goma , potentially leading to further clashes as the deadline passed . At the United Nations , a spokesman for Secretary-General Ban Ki-moon urged the rebels `` to immediately lay down their arms in accordance with the agreements reached in Kampala and comply with the immediate withdrawal of their forces from Goma . '' The spokesman , Eduardo del Buey , said Ban urged the parties to continue talks `` to address the fundamental causes of the conflict . '' He said Ban will also make sure that the U.N. peacekeeping mission MONUSCO is able `` to respond to he evolving challenges . '' But he added , `` The mandate of MONUSCO is to protect civilians . It is not to fight the M23 on its own . That is he responsibility of the Congolese armed forces , and the maintaining of security is the primary responsibility of the Congolese police . '' The M23 group was named for a peace deal reached on March 23 , 2009 , which it accuses the government of violating . Rene Abandi , a spokesman for the M23 group , told reporters on the sidelines of the conference Saturday that the rebels ' main aim was to force Congolese President Joseph Kabila to agree to talks . `` We want talks over human rights and insecurity ( involving ) issues contained in the 2009 truce , which he , Kabila , has refused to implement , '' Abandi said . The outstanding issues include positions in the national army , an equitable distribution of resources and infrastructure development in eastern Congo , Abandi said . Kabila was one of the African leaders who devised a new game plan at the Great Lakes region summit in Kampala over the weekend . But the consortium did n't just call for concessions from the rebels : The group 's statement also called on the Congolese government to listen to and resolve the grievances of the rebels , who took control of Goma on Tuesday after days of fighting with government forces . In Goma itself , citizens are getting frustrated with M23 , because many shops and all banks have n't opened , and only a few students have trickled back to school . International organizations such as Oxfam and World Vision and the United Nations have been forced to abandon operations in eastern Congo . Now , aid groups are warning of escalating risks of disease and abductions facing victims fleeing the violence and uncertainty . CNN 's David McKenzie and Joseph Netto contributed to this report .
NEW : The United Nations calls on rebels to stop fighting . M23 rebels occupying the city of Goma , Democratic Republic of Congo , refuse to leave . African leaders gave the rebel group until midnight Tuesday to withdraw . The rebels want to talk with Congolese president about breaches of a 2009 peace treaty .