A gunman on Saturday opened fire at a Jewish synagogue in the US city of Pittsburgh, killing at least 11 people and injuring several others including three policemen, in the deadliest “anti-Semitic attack” in America in years.

The shooter was identified as 46-years-old Robert Bowers. He surrendered after he was injured during an exchange of fire with the police, according to local media reports.

No children were among the fatalities and the injured include four police officers.

The initial call to 911 was made around 9.54 a.m. and officers were dispatched to the scene within a minute.

The shooting occurred at the Tree of Life Congregation in Pittsburgh’s Squirrel Hill neighbourhood.

Police said the gunman, a heavy-set white male with a beard, surrendered and is in custody. The shooting occurred during a baby-naming ceremony at the synagogue, according to reports.

The FBI is investigating this as a “hate crime”. Before opening fire, the shooter reportedly yelled, “All Jews must die!”

Attorney for Pennsylvania’s Western District Scott Brady confirmed the suspect is Robert Bowers, reportedly a 46-year-old man from Pittsburgh.

Bowers’ social media posts were reportedly rife with anti-Semitic content.

Brady said Bowers’ actions “represent the worst of humanity” and criminal charges against him could be filed as early as Saturday.

President Donald Trump described this as a devastating situation.

“Events in Pittsburgh are far more devastating than originally thought,” Trump said as he reiterated that those responsible for such mass shooting be given death penalty.

He was considering cancelling an election campaign rally in Illinois in the aftermath of the shooting that has shocked all Americans.

“What happened today is a horrible, horrible thing. It looks definitely like it’s an anti-Semitic crime. That is something you wouldn’t believe could still be going on,” Trump told reporters after he stepped off Air Force One in Indianapolis.

“It would seem to be an anti-Semitic crime,” said Trump, whose daughter Ivanka Trump is married to Jew Jarred Kushner.

“A lot of people killed, a lot of people very badly wounded. They say as a crime scene it’s one of the worst that some professionals that have seen many many crime scenes, they say it’s one of the worst,” Trump said.

UN Secretary-General Antonio Guterres on Saturday strongly condemned the shooting at the synagogue in Pittsburgh, said his spokesman.

Guterres was shocked at the bloody shooting that killed 11 people. He expressed his deepest condolences to the families of the victims, said Stephane Dujarric, the spokesman, in a statement.

“The shooting in Pittsburgh is a painful reminder of continuing anti-Semitism. Jews across the world continue to be attacked for no other reason than their identity. Anti-Semitism is a menace to democratic values and peace, and should have no place in the 21st century,” said the statement.

(With inputs from agencies)