KINSHASA (Reuters) - Clashes between opposition protesters and security forces broke out in parts of Democratic Republic of Congo on Saturday, killing at least one, a day after election authorities named incumbent President Joseph Kabila winner of a disputed poll. Gunfire rang out in some cities, including the capital Kinshasa, after Kabila's main challenger, Etienne Tshisekedi, said he rejected the official results and declared himself the new leader of the vast central African state. "Since last night it has been very bad, we haven't been able to sleep because of the gunfire," said Tresor Nkuna, a resident of Kinshasa, an urban sprawl of 10 million people. "We don't know when it'll stop, it's very violent," he said. Many other parts of Kinshasa were quiet with people staying indoors, witnesses said.