A gunman opened fire at a synagogue in the US city of Pittsburgh on Saturday, reportedly killing at least four people and injuring others before being taken into custody.
Officials did not immediately confirm a motive for the attack at the synagogue, where dozens of people were understood to be celebrating Shabbat services on the Jewish sabbath, and which comes with the United States witnessing a sharp spike in anti-Semitic incidents.
US television networks reported that at least four people had died, while the local CBS affiliate reported that eight people were dead.
A police spokesman addressing reporters at the scene confirmed "multiple casualties" and said three officers where shot before the shooter was taken into custody.
The condition of the officers was not immediately clear.
Police were still clearing the building, the official said.
A woman at the scene told CNN that her daughter was with others who ran down the stairs and barricaded themselves in the basement of the synagogue after hearing shots.
"They're safe, but they kept hearing them firing and everything else," she told the television network.
CNN broadcast footage of police cars, ambulances and a police SWAT team outside the place of worship.
The Tree of Life Synagogue is about five miles (eight kilometers) east of downtown Pittsburgh in the residential Squirrel Hill neighborhood.
Pittsburgh's Public Safety department, which includes the police, declared earlier that an active shooter was in the area near the synagogue, urging residents to stay away.
"There are multiple casualties," the Pittsburgh Post-Gazette quoted Police Commander Jason Lando as saying.
It is the latest shooting incident in the United States, where gunmen regularly cause mass casualties and firearms are linked to more than 30,000 deaths annually.
Michael Eisenberg, past president of the Tree of Life synagogue, told CNN that the door would typically have been open on Saturdays with religious services going on. He said police are normally deployed only on High Holy Days -- the holiest annual Jewish religious holidays.
He said security was a "major concern" during his stint as president, and active shooting situations and active shooter trainings were conducted, "if something horrific like this happened.
The motive of the shooting was not immediately clear, but anti-Semitism and hate crimes have been on a rise in the United States in recent years.
On Friday, Jonathan Greenblatt, chief executive and national director of the Anti-Defamation League, published an op-ed in the Washington Post newspaper decrying a rise of anti-Semitism on college campuses.
Such episodes nearly doubled last year, reflecting a nationwide spike in anti-Semitism, when incidents increased 57 percent, to 1,986, from 1,267, according to the ADL.
Squirrel Hill has historically been the center of Jewish life in the greater Pittsburgh and is home to 26 percent of all Pittsburgh-area Jewish households, according to a study from Brandeis University.
More than 80 percent of the neighborhood's residents said they had some concern or were very concerned about rising anti-Semitism, found the 2017 study.
The Tree of Life congregation was founded more than 150 years ago and in 2010 merged with the five-year-old Or L'Simcha congregation.
US President Donald Trum tweeted, "Watching the events unfolding in Pittsburgh. Law enforcement on the scene. People in Squirrel Hill area should remain sheltered. Looks like multiple fatalities."
Mr Trump later hit out at what he called "hate" in America.
"It's a terrible, terrible thing what's going on with hate in our country frankly, and all over the world," he told reporters as he left for a series of campaign events in Indiana and Illinois.
"Something has to be done," said the president. "When people do this, they should get the death penalty."
As local media reported the death toll in Pennsylvania could be as high as eight people, Mr Trump said the shooting appeared "far more devastating than anybody originally thought."