Casualties on both sides as Congolese soldiers and UN forces clash with rebels The front line is only 9 miles (15 kilometres) north of Goma. M23 rebels briefly overtook the city late last year, and Congolese and U.N. troops have been battling to dislodge rebels from heights overlooking the city since Wednesday. Observers estimate that Congolese forces have advanced less than a mile since Wednesday and have yet to achieve their immediate objective - cutting off M23 from a border crossing where the rebel group is believed to get supplies from neighbouring Rwanda. The M23 is made up of hundreds of Congolese soldiers mostly from the Tutsi ethnic group who deserted the national army last year after accusing the government of failing to honour the terms of a deal signed in March 2009. Many of the movement's commanders are veterans of previous rebellions backed by Rwanda, which vigorously denies allegations that it has been supporting and reinforcing M23. The rebels briefly seized Goma, a city of nearly 1 million people, last November, before withdrawing under international pressure and in return for a promise of peace talks with the government. The talks in neighbouring Uganda have frequently stalled and appear to have made little progress since March. The renewed fighting erupted Wednesday, breaking a three-week lull in the region. On Thursday, the new U.N. intervention brigade that was created in March with a strong mandate to protect civilians fired for the first time on rebel positions. "We are using artillery, indirect fire with mortars and our aviation, and at the moment we have troops in the front line alongside (the government forces)," Gen. Dos Santos Cruz, the U.N. force commander in Congo, said Saturday. In Washington, the state department condemned the actions of the M23, voicing concern over "credible U.N. reports that the M23 has fired into Rwandan territory." In a statement issued Sunday, it called on the rebel group to immediately cease hostilities, disarm and disband. There has been widespread scepticism, however, in Congo that the intervention brigade will be a game-changing addition to the existing U.N. force, which stood by when M23 fighters captured Goma late last year. On Saturday, scores of Goma residents took to the streets in anger over a series of rocket and mortar attacks that have left at least seven civilians dead in recent days. Two other residents were killed during the demonstration, and the U.N. called for a joint investigation.