US President Barack Obama expressed solidarity Monday with Denmark and vowed to confront anti-Semitism and assaults on freedom of expression together with Copenhagen.
Faced with the spectacle of European Jews being again targeted by extremists, just over a month after similar attacks in Paris, governments were scrambling to reassure their Jewish communities.
The first victim, 55-year-old filmmaker Finn Nørgaard, was killed when a gunman opened fire during a debate on free speech on Saturday which featured controversial Swedish artist Lars Vilks.
The same attacker then targeted Copenhagen's main synagogue, killing 37-year-old Dan Uzan.
During a telephone call, Obama and Danish Prime Minister Helle Thorning-Schmidt "agreed on the need to work together to confront attacks on freedom of expression as well as against anti-Semitic violence," the White House said in a statement.
It said Obama offered his condolences for the victims and expressed "American solidarity with our Danish allies."
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Obama also welcomed Denmark's participation in a three-day, high-level summit he is hosting this week to share best practices and agree on a plan of action to counter radicalization, recruitment and incitement to violence, the White House said.
Representing Denmark will be Aarhus mayor Jacob Bundsgaard, who will discuss the city's controversial jihadist rehab programme and anti-radicalization efforts.
A senior US official also confirmed that the FBI are helping Danish authorities probe the attacks, though the official declined to say what kind of help the US was providing.