On Friday night, extremists wearing explosive belts and carrying automatic weapons attacked several venues across Paris, killing 129 and injuring dozens of people at restaurants, the Bataclan concert hall and in the vicinity of the Stade de France sports arena. According to preliminary reports some of the attackers were thought to have entered Europe disguised as refugees, a result of weak border control in some EU member states.
"We should put the [Schengen] agreement to rights. If the agreement cannot work as it should, then, of course, we should reinstate border controls at internal borders of the Member States," Sipila said on Saturday, quoted by the Finnish broadcasting company Yle.
The prime minister added that discussions about resuming border checks between Schengen members has happened before.
Soon after the Saturday attacks Helsinki increased the readiness of its police and tightened border controls.
The Schengen area provides for visa-free movement between 22 EU member states, as well as four non-EU members Switzerland, Norway, Iceland and Lichtenstein. States participating in the Schengen regime eliminated border checks between members and increased border control with non-Schengen countries.