BERLIN — Three Syrians who entered Germany as migrants have been arrested on suspicion of belonging to the Islamic State and may have had links to those who carried out the Paris terrorist attacks last year, the authorities said on Tuesday.  Thomas de Maizière, the German interior minister, said that the travel documents the men were carrying when they were arrested on Tuesday had been issued by the same authority as ones found on some of the men who carried out the attacks in and around Paris in November. The authorities also said that the three Syrians appeared to have used the same smugglers to enter Germany and to apply for asylum as some of those involved in the terrorist assaults in France.  “It could be that this was a sleeper cell,” Mr. de Maizière told reporters.  Prosecutors said in a statement that they believed the three came to Germany in November to carry out a planned attack for the group, also known as ISIL or ISIS, or to await instructions for one.  There was no indication the three had been planning a specific attack, according to prosecutors, who gave no further details about possible targets. But they said they had sufficient evidence to arrest the men on suspicion of membership in a foreign terrorist organization.  German security authorities have been on high alert since two young men who entered the country as migrants, and who had received benefits funded by German taxpayers, carried out separate attacks in Bavaria in July, wounding dozens. Both attacks appeared linked to or inspired by the Islamic State, the authorities said.  The three men arrested on Tuesday, in the northern state of Schleswig-Holstein, were identified only by their first names and last initials, in keeping with German privacy laws: Mahir al-H., 17; Mohamed A., 26; and Ibrahim M., 18. They entered the country in November by traveling through Turkey and Greece and had been living in refugee shelters north of Hamburg, the German news media reported.  Prosecutors said they suspected that Mahir al-H. had joined Islamic State militants in Raqqa, Syria, at some point before September 2015, and that he had received training in the use of weapons and explosives.  In October, he and the two other suspects “pledged to an Islamic State operative responsible for operations and attacks outside of Islamic State-held territory to travel to Europe,” where they were either to carry out a planned attack or await instructions, prosecutors said. “For this, they were supplied with passports issued by the Islamic State and tens of thousands of dollars, as well as mobile phones with previously installed communication programs.”  Germany admitted more than a million migrants last year, a move that has led to a rise in anti-immigrant sentiment and strengthened political forces to the right of Chancellor Angela Merkel’s center-right conservative bloc.  The federal criminal police have reported receiving 415 tips about possible terrorists hiding among refugees, but they said that only 63 had been serious enough to require an investigation.
They are thought to have arrived in the country among hundreds of thousands of migrants and to have had links to those behind the Paris attacks lacks year.