A new U.N. combat brigade formed to attempt to neutralize armed groups in the Democratic Republic of Congo (DRC) fired artillery at M23 rebels threatening the eastern border city of Goma, U.N. and Congolese military officers said Friday. It was the brigade's first clash with M23 in support of DRC government forces. The U.N. brigade, composed of soldiers from South Africa, Tanzania, and Malawi, was created by the Security Council in March. Fighting continued for a third consecutive day near Goma, a city of about a million people on the border with Rwanda, after a relative lull in the 18-month-old M23 rebellion. Goma was briefly seized by the M23 last year, and the United Nations pledged last month to prevent the rebels from positioning close to the city. But the rebels this week entered a security zone around Goma that had been established by the U.N. Intervention Brigade earlier this month, and at least two people were killed when three shells landed in the city center. U.N. Lieutenant Colonel Felix Basse said another M23 shell hit near Munigi, outside of Goma, where a U.N. peacekeeper base is located, causing some civilian casualties. "Of course, we responded with artillery, as we cannot accept any threat to the population. That's why we retaliated," he told Reuters by telephone from Goma.