Kinshasa - Clashes broke out on Monday in the east Democratic of Republic of Congo city of Goma between police and demonstrators opposed to President Joseph Kabila's sustained grip on power and demanding elections.The youth movement Struggle for Change (Lucha) urged followers and sympathisers to turn out for "a peaceful march" around the country "to say 'No' to Mr Kabila's life presidency and demand elections before the end of this year".Several opposition coalitions and prominent figures including Moise Katumbi, business leader and former governor of the southern Katanga province, expressed support for the marches, timed to mark the July 31 date given by the Independent National Electoral Commission (CENI) to conclude the registration of voters.Police arrested a dozen demonstrators in Goma, the capital of North Kivu province, AFP's local correspondent reported. But protesters continued to throw stones at police and build makeshift barricades when the police fired tear gas to disperse them.A priest in the North Kivu town of Butembo said that 11 protestors "were brutally roughed up, one was bleeding".In Bukavu, capital of South Kivu province, demonstrators gathered on Independence Place but were dispersed by police using tear gas.No arrests were seen among protesters, an AFP correspondent said, but at around 0900 GMT police detained two journalists from the private television channel Canal Futur, impounding their equipment. A third journalist, from the local state TV station, was briefly held then released with his equipment.In the national capital Kinshasa, a metropolis of more than 10 million people, riot police were deployed on the strategic Triumphal Boulevard and around the parliament buildings. Opposition leaders had called for a peaceful march to start at this point and proceed to the CENI headquarters.Police were patrolling the surrounding area on foot and in vehicles.When Kabila refused to stand down in September last year in accordance with the constitution at the end of his second elected five-year term, more than a dozen people were killed in Kinshasa protests.A political agreement was reached on December 31, 2016, to hold elections by the end of 2017, under the aegis of the influential Roman Catholic church. On July 7, however, the CENI chairperson announced that it would not be possible to organise elections in the vast and troubled country in time for the end of this year.