BERLIN - The deadly attacks in Paris have sparked a debate in Germany on Chancellor Angela Merkel's refugee policy and how to get a better overview of the people entering the country.Islamic State on Saturday claimed responsibility for the coordinated assault by gunmen and bombers that killed 127 people in Paris. President Francois Hollande said the attacks amounted to an act of war against France, and called for "merciless" retaliation against those responsible.Merkel said Germany would help France to hunt down the perpetrators and backers of the attacks, promising a joint battle to defend European values."This attack on freedom is not only aimed against Paris. It's aimed against us all," Merkel said. "We know that our free life is stronger than terror."German authorities increased security measures at public places such as train stations and Interior Minister Thomas de Maiziere said more extremists could be on the run.He also confirmed that German police had contacted French authorities after arresting a man from Montenegro in Bavaria on Nov. 5, who was apparently heading to Paris in a car carrying guns and explosives.Asked about reports that at least one of the attackers in Paris came from Syria, De Maiziere said French authorities were still investigating and it was up to them to inform the public."But I make the urgent plea, as interior minister and as a responsible politician of this country, that there shouldn't be any hasty links made to the refugee debate," he added.Only hours before, Bavarian state premier Horst Seehofer, leader of Merkel's sister party, the Christian Social Union (CSU), had urged better protection of Germany's frontier and called for stricter controls at Europe's external borders."In light of the increased migration to Germany, we have to know who is driving through our country," said Seehofer, who has repeatedly criticized Merkel for her open-door approach in the refugee crisis.But Vice Chancellor and Economy Minister Sigmar Gabriel warned against making Germany less welcoming to refugees in response to the attacks."We should not make them suffer for coming from regions from which the terror is being carried to us," he said."As a state under the rule of law, as a free state, we are always vulnerable. Still, we want to remain an open country, an open society," said Gabriel, who is also head of the Social Democrats (SPD), Merkel's junior coalition partner.Germany reimposed border controls on Sept. 13 and decided to extend them beyond an initial limit of two months foreseen by Schengen rules, using a clause that permits stretching checks to a maximum of six months.Frauke Petry, head of the anti-immigrant Alternative for Germany (AfD), said on Twitter that Seehofer was advertising for her party with his calls for stricter border controls. Seehofer rejected the assertion. "We have nothing at all to do with the right-wing boneheads," he said.