A man armed with an assault rifle and three handguns kills 11 and injures six in the Squirrel Hill area of the city.

A suspect has been taken into custody in Pittsburgh, in the US state of Pennsylvania, after a shooting at a synagogue that killed at least 11 people and injured six others, including four police officers, according to authorities.

Wendell Hissrich, the city’s public safety director, said Saturday’s suspected attacker was at a hospital in fair condition with multiple gunshot wounds.

FBI special agent Bob Jones said the attacker used an assault rifle and three handguns inside the Tree of Life Synagogue in the Squirrel Hill neighbourhood.

The attacker was leaving when he met an officer, Jones said.

Local television station KDKA said the suspect in custody was a “white male”. A law enforcement official, who spoke to The Associated Press news agency on condition of anonymity, identified the detainee as Robert Bowers, a man in his 40s.

An earlier social media post by Bowers said: “[A Jewish refugee organisation, the Hebrew Immigrant Aid Society] likes to bring invaders in that kill our people. I can’t sit by and watch my people get slaughtered. Screw your optics, I’m going in.”

The comment was posted on Gab, a Philadelphia, Pennsylvania-based social networking service created as an alternative to Twitter.

Bowers also recently posted a photo of a collection of three semi-automatic handguns he titled “my glock family,” a reference to the firearms manufacturer.

He also posted photos of bullet holes in person-sized targets at a firing range, touting the “amazing trigger” on a handgun he was offering for sale.

In a statement, Gab.com confirmed the profile belonged to Bowers.

“Gab took swift and proactive action to contact law enforcement immediately,” it said.

“We first backed up all user data from the account and then proceeded to suspend the account. We then contacted the FBI and made them aware of this account and the user data in our possession.”

Al Jazeera’s John Hendren, reporting from Washington, DC, said the shots began at about 10am local time as worshipers were gathering for Sabbath (Saturday) services.

“There were perhaps 60 to 100 people inside there,” he said.

Local TV news footage showed police at the location with rifles [Gene J Puskar/AP]

The Tree of Life synagogue describes itself on its website as a traditional, progressive and egalitarian congregation. Few other details were immediately available.

The tree-lined residential neighbourhood of Squirrel Hill close to the city centre is the hub of Pittsburgh’s Jewish community.

Local TV news footage showed police at that location with rifles and wearing helmets and other tactical gear.

Paramedics also were stationed near the synagogue and police vehicles were blocking some streets in the area.

US President Donald Trump took to Twitter to say he was watching events in Pittsburgh: “Looks like multiple fatalities. Beware of active shooter. God bless all!”

Later, he told reporters: “It’s a terrible, terrible thing what’s going on with hate in our country frankly, and all over the world. Something has to be done. When people do this, they should get the death penalty.”

Pennsylvania Governor Tom Wolf called the shooting an “absolute tragedy”.

“We must all pray and hope for no more loss of life,” Wolf said. “But we have been saying ‘this one is too many’ for far too long. Dangerous weapons are putting our citizens in harm’s way.”

Saturday’s shooting incident is the latest in the United States, where firearms are linked to more than 30,000 deaths annually.