BARCELONA (Reuters) - Police are investigating the role of foreign citizens in riots over the jailing of a Spanish rapper that have rocked Barcelona for the past two weeks, a police source said. Catalan regional police detained six Italians and one French citizen on Saturday. On Monday they inspected two houses outside Barcelona which were illegally occupied and where at least some of the detained appeared to live, the source told Reuters. Police have arrested more than 100 people since the protests over the jailing of rapper Pablo Hasel erupted on Feb. 16. The exact role of the foreigners was unclear. Miquel Samper, interior affairs minister in the Catalan regional government, told reporters on Monday that police face an “unprecedented complex situation” as the protesters could meet and take action quickly. Some were foreign anarchists, he said. The protests escalated on Saturday. A police van was set on fire with an officer inside who managed to escape. Protesters also smashed the fronts of shops and banks, including along Barcelona’s central La Rambla boulevard. One of the arrested foreigners was related to the van attack, the source said. Hasel has been sentenced to nine months in prison after being convicted of glorifying terrorism and insulting the monarchy, galvanizing defenders of freedom of speech and sparking protests. The conviction also prompted the government to announce it would relax free speech legal restrictions. He was convicted for lyrics and tweets that included references to Basque separatist group ETA, calling Spain’s former King Juan Carlos a mafia boss, and likening Spanish judges to Nazis. Samper said on Sunday a group of 150 and 200 protesters were behind the demonstrations’ escalation into riots, some of whom threw petrol bombs, and they had engaged in direct violence with no apparent reason. Business organizations and police unions have demanded a firmer government action against the riots after damages to property already amounts to over two million euros. One protester lost an eye from the impact of a foam bullet.