Iran FM gives condolences to victims of synagogue massacre

"Extremism and terrorism know no race or religion and must be condemned in all cases," Zarif wrote on Twitter.

"The world deserves better than to have to live with weaponized demagoguery. 

"Thoughts and prayers with victims of terrorist attack on Pittsburgh synagogue and their loved ones," said Zarif whose country's ties with the United States have been severed since 1980.

Eleven elderly people were killed at the Tree of Life synagogue in Pittsburgh on Saturday by a gunman who later told police he "wanted all Jews to die".

Unchecked hatred

The Pittsburgh synagogue attack is the deadliest anti-Semitic attack in recent US history, and has sparked a flood of international condemnation and warnings about the rise of hate speech. 

The Tree of Life Synagogue, whose congregation was founded more than 150 years ago, is located in the Squirrel Hill neighbourhood that is historically the heart of Jewish life in greater Pittsburgh.

But the shockwave was felt much further, throughout America's Jewish community, the largest outside Israel.

In a statement, the United States Holocaust Memorial Museum said it "reminds all Americans of the dangers of unchecked hatred".

The United States is witnessing a sharp spike in anti-Semitic incidents, surging 57 percent from 2016 to 2017, to 1,986 from 1,267, according to the Anti-Defamation League, a civil rights group which has tracked anti-Semitism in the United States since the 1970s.

Saturday's attack also comes at a time of heightened political tensions - a day after a Trump supporter from Florida was arrested for mailing explosive devices to Democrats and liberals, setting the country on edge ahead of close-fought elections on 6 November.