Federal prosecutors said on Monday that Ms. Reker’s 44-year-old assailant, who was known to have past ties to right-wingers, openly stated that he wanted to hurt someone handling refugee affairs.

On Thursday, Mr. de Maizière did not refer publicly to the danger of a possible attack as he toured a new center in Bamberg, set up by the state of Bavaria, to house migrants whose chances of winning asylum in Germany are low. He praised the new repatriation center as part of an effort to speed up deportations, which could free up more room for the refugees who arrive daily by the thousands, straining resources throughout the country.

Meanwhile the authorities issued new figures for the number of attacks on asylum facilities, showing a steep rise from last year. The Federal Criminal Police Office said almost 580 such attacks had been recorded so far this year, compared with 198 in all of 2014, when about 200,000 people applied for asylum. The total applying this year could exceed one million, although officials have cautioned that accurate numbers for new arrivals are hard to ascertain.

The news of the raids in Bavaria suggested that the authorities not only wish to show the far right that they are keeping close watch, but also to prove to critics that they are not blind to right-wing extremism. From 2000 to 2007, a series of 10 killings of immigrants long went unsolved before a right-wing group was suspected. The only surviving member has been on trial since 2013 in Munich, with the proceedings likely to stretch into next year.

The Bavarian police and the Bamberg prosecutors said that the 11 men and two women detained on Wednesday had ties to right-wing circles and “hooligans” nationwide. The group had recently shown “a heightened readiness to use violence and increasing potential for aggression,” the police and prosecutors said in their statement. It cited without further detail an assault on three passers-by in Bamberg in May in which at least one man assaulted and injured the trio and several violent clashes at an unnamed pub in the town.

Among the weapons confiscated were a loaded gun and several unloaded weapons, plus ammunition for all, the police said.

The 13 people in custody range from 21 to 36 years old; the three who have been charged are 23, 24 and 29. At least some of the 10 others detained are likely to be formally arrested and charged, police said.