Authorities believe the mosque was used as a hub to funnel people and arms to conflict zones.
The Interior Ministry estimates that around 3,500 anti-refugee incidents took place last year.
The nomination of former European Parliament president Martin Schulz sparked a revival in support for the party.
The Chancellor also said it was critical to include Muslim countries in the fight against terrorism.
The Euroskeptic political scientist has Brussels politicians worried.
Majorities of people in eight countries think immigration from mainly Muslim countries should be stopped.
The German Chancellor needs the support of the controversial Law and Justice government.
The cover of the German magazine depicts the president beheading Lady Liberty.
Trump and his policies, from questioning the value of NATO and free trade to banning Muslim refugees, came up repeatedly in discussions in Malta on external "challenges" facing the Union.
The German chancellor must preserve a deal with Ankara that limits refugee flows into Europe.
Former European Parliament president Schulz took over his party to turn its flagging performance around.
Martin Schulz said that Europe had to stand up to defend liberal values.
The German Chancellor will discuss the situation in east Ukraine.
Merkel reminded Trump on Saturday that the Geneva Conventions require the international community to take in war refugees on humanitarian grounds.
A full third of Trump supporters hold a favorable view of Putin.
Schulz is Merkel's nearest competitor for the German chancellorship.
Schulz will stand as the center-left Social Democratic Party (SPD) candidate for Chancellor in the poll scheduled for September.
Police arrested the Austrian suspect, a 17-year-old with Albanian roots, after tip-offs.
The head of the far-right party in Thuringia described the memorial as a "monument of shame" in Dresden.
"I thought frankly it was inappropriate for a president-elect of the United States to be stepping into the politics of other countries in a quite direct manner," Kerry told CNN.