Chancellor Angela Merkel dismissed suggestions that the arrival of 1.1 million migrants in Germany last year has brought Islamic State terrorism to the country.
"Terrorism by Islamic State is not a phenomenon that arrived with the refugees, it is one that was there before," Merkel said late Wednesday at a campaign event in the eastern state of Mecklenburg-Vorpommern, which is holding a state election on September 4.
Germany has been on high alert since two terrorist attacks last month - an axe-and-knife attack on a commuter train and a suicide bombing outside a music festival - were claimed by Islamic State. Both were carried out by asylum seekers.
The right-wing Alternative for Germany (AfD) party and critics in Merkel's own conservative political bloc argue that her policy of open borders has created a national security problem in the country.
In Mecklenburg-Vorpommern, the AfD is polling at around 18 per cent while Merkel's Christian Democrats (CDU) are at 23 per cent.