( CNN ) -- Northern Ireland 's top police officer on Saturday condemned violent clashes that left 56 of his officers injured as `` mindless anarchy '' -- and warned that many arrests will follow . The disorder broke out in central Belfast as loyalists held counter-protests Friday evening against a nationalist march . The Police Service of Northern Ireland said Friday that 26 officers had been injured , with five of them needing hospital treatment . But that tally more than doubled on Saturday . Seven arrests have been made so far , police said . Warning of more to come , Chief Constable Matt Baggott said , `` Significant custodial sentences will be handed down in the weeks and months that follow -- the prisons will be bulging , sadly . '' He said `` intense violence '' had been directed toward the police , and that they had shown `` immense courage '' in standing their ground to stop the anarchy spreading . `` I know the majority of the population will stand with me in condemning those who scarred the reputation of our beautiful city last night , '' he said . `` Those people had no intention of peaceful protest . They lack self respect and they lack dignity . '' Police were braced for further trouble on Saturday . More parades are scheduled to take place across the country , organized by the Apprentice Boys , a Protestant group . The main demonstration is in Londonderry . The disorder broke out in Belfast 's main shopping district , as loyalists blocked the intended route of the nationalist march , which was eventually redirected . Assistant Chief Constable George Hamilton , who led the policing operation , said about 1,200 people had gathered `` and it was evident that many of them had violent intent . '' His officers were pelted with whatever came to hand , he said , including paving slabs pulled up from the street , bricks and lengths of scaffolding . `` There was nothing lawful about this protest . There was nothing peaceful about it . It was sheer thuggery , '' he said . Plans for peaceful protests had been registered with the Northern Ireland Parades Commission , which rules on which marches are allowed to take place and which are banned , in an effort to keep friction to a minimum . Friday 's pro-Irish nationalist march followed heightened tensions during some loyalist marches this summer . Hundreds of parades take place across Northern Ireland each year , the majority involving the Protestant Orange Order and associated organizations . Most parades pass off peacefully , but when members of one community march near or through neighborhoods dominated by another , violence sometimes results .
NEW : ` ` Those present had no intention of peaceful protest , '' said top police officer . Police say 56 officers were hurt in violent clashes with loyalists in Belfast . The violence broke out as people staged protests against a nationalist government . Belfast 's main shopping centre was the scene of the violence .