Themes of inclusion and compassion dominated the speeches delivered to an overflow crowd of some 2500 at the University of Pittsburgh's Soldiers and Sailors Hall on Sunday, as speakers decried the rise of toxic political discourse widely seen as creating an atmosphere conducive to violence.

Tree of Life Rabbi Jeffrey Myers elicited shouts of "vote" from the audience as he called on political leaders, starting with "those in the room," to help put an end to hate speech.

"My words are not intended as political," he said from the stage. "My mother always taught me that if you don't have anything nice to say, don't say it."

The "Stronger Together" service opened with a performance by a Baptist gospel choir and included remarks by Christian and Muslim clergy, but it was largely led by Meyers and two fellow rabbis representing the three Jewish congregations who used the synagogue targeted in Saturday's carnage.

"What happened yesterday will not break us. It will not ruin us. We will continue to thrive and sing and worship and learn together and continue our historic legacy in the city with the friendliest people that I know," said Rabbi Jonathan Perlman, choking back tears.

Three members of his congregation were among those killed when a man armed with an assault rifle and three handguns on Saturday stormed the Tree of Life temple in the city's heavily Jewish Squirrel Hill neighbourhood yelling "All Jews must die" as he opened fire on worshippers.

In addition to the 11 mostly elderly victims who were killed, six people, including four police officers, were wounded before the suspect was arrested.

Two of the surviving victims remained hospitalised in critical condition.

The massacre marked the deadliest attack ever on America's Jewish community, according to the Anti-Defamation League and Jewish Council for Public Affairs.

Robert Bowers, 46, who has a history of posting anti-Semitic messages online, has been charged under federal hate crime statutes and could face the death penalty if convicted.

"This is the darkest hour in our city's history," Pittsburgh Mayor Bill Peduto declared during Sunday's service.

"But here's another thing about Pittsburgh. We are resilient. We will work together as one. We will defeat hate with love. We will be a city of compassion and we will be welcoming to all people," he said to cheers.

The names of the dead were released hours earlier. They included David Rosenthal, 54; his brother Cecil Rosenthal, 59; Sylvan Simon, 86, and his wife Bernice Simon, 84; Joyce Fienberg, 75; Richard Gottfried, 65; Jerry Rabinowitz, 66; Daniel Stein, 71; Melvin Wax, 88; and Irving Younger, 69. The eldest victim was Rose Mallinger, 97.

Rabinowitz was a family physician who initially escaped the attack only to be killed when he returned to render aid to the wounded, according to a Wall Street Journal op-ed column by Pittsburgh carpet salesman Lou Weiss, who knew five victims personally.

Australian Associated Press