The French leader said in a tweet that his thoughts were with the victims and offered his support to the grieving families.
I strongly condemn this horrific act of antisemitism in Pittsburgh. All my thoughts to the victims and my sympathy for their beloved ones. https://t.co/pL9z72PdlLEmmanuel Macron (@EmmanuelMacron) 27 octobre 2018
Interior Minister Christophe Castaner said on social media that he had told local authorities to step up protection of synagogues and "other planned events" from Sunday.
Castaner announces tighter security this weekend
Je viens de demander aux Préfets de renforcer dès demain la vigilance autour des synagogues et des événements programmés ce week-end.Christophe Castaner (@CCastaner) 27 octobre 2018
"Anti-Semitism kills and anti-Semitism has no borders. The terrible attack in Pittsburgh is tragic proof," Castaner said in another tweet.
"In Pennsylvania, as in our own country, we remain united against hate," he added, expressing solidarity with the American people.
France's half-million-plus Jewish community is the largest in Europe.
It has been hit by a wave of emigration to Israel in the past two decades, partly due to a rise in anti-Semitic attacks in predominantly immigrant neighbourhoods.
Attacker detained after firefight
The Pittseburgh took place during a baby-naming ceremony at the Tree of Life synagogue on Saturday morning when a man later identified as 46-year-old local resident Robert Bowers burst into the building and opened fire.
He was reported to be yelling "All Jews must die!"
Taken into custody after a firefight with police, the suspect was transferred to hospital.
US prosecutors later charged him with 29 counts of federal crimes of violence and firearms offenses, including 11 counts of using a firearm to commit murder and 11 counts of obstructing the exercise of religion resulting in death.
Speaking to supporters at an election rally in Illinois, President Donald Trump denounced "a wicked act of mass murder" and drew loud cheers as he vowed to fully enforce the death penalty for such crimes.
He told reporters in Indianapolis, where he was attending an event organised by uture Farmers of America, that the suspect was “no supporter of mine” and said he would visit Pittsburgh, without specifying when.
The shooting prompted reactions from leaders across the globe:
- Israeli Prime Minister Benjamin Netanyahu declared himself "heartbroken and appalled". "We stand together with the American people in the face of this horrendous anti-Semitic brutality," he said in a video message.
- German Chancellor Angela Merkel slammed an act of "blind anti-Semitic hatred," saying: "We all have to stand up against anti-Semitism, everywhere."
- UN Secretary General Antonio Guterres called for a united front "to roll back the forces of racism, anti-Semitism, Islamophobia and other forms of hatred, bigotry, discrimination and xenophobia gaining strength in many parts of the world".