Government forces have launched a new offensive against rebels in the Democratic Republic of Congo, seizing a town held by a renegade general, the United Nations and army sources said on Friday. Dissident army officer General Laurent Nkunda seized large swathes of eastern Congo near Rwanda after launching a rebellion in May. His forces captured the border town of Bukavu before withdrawing to a base 120 km (75 miles) to the north. "He (Nkunda) attacked us again, bombing our positions, so we have reacted," a Bukavu-based army officer told Reuters on Friday. "We have retaken Nyabibwe, 100 km north of Bukavu, and we are going all the way to (Nkunda's base at) Minova." Nkunda, a hardliner from former Rwandan-backed rebel group RCD-Goma, was not immediately available for comment. Diplomatic sources in Kinshasa said Rwanda had expressed concern about the troop movements. Congo is struggling to emerge from a five-year war that, at its height, sucked in six neighbouring countries and killed 3 million people, mostly through hunger and disease. Recent fighting in the east has raised fears of a return to war. The U.N. mission in Congo said it had not yet independently confirmed the offensive, but had received numerous reports that government troops were heading north. --More 2329 Local Time 2029 GMT