The funeral on Saturday for 86-year-old Ruth Whitfield - the oldest of the 10 people killed in the attack two weeks ago - included an impromptu speech by Harris.

Harris told the mourners this is a moment in time for "all good people" to stand up to the injustice that happened at the Tops Friendly Market on May 14, as well as at the Robb Elementary School in Uvalde, Texas, and in other mass shootings.

"This is a moment that requires all good people, all God-loving people to stand up and say we will not stand for this. Enough is enough," said Harris, who was not scheduled to speak and came to the microphone at the urging of the Reverend Al Sharpton.

"We will come together based on what we all know we have in common, and we will not let those people who are motivated by hate separate us or make us feel fear."

Following the funeral, Harris visited a memorial outside the supermarket.

President Joe Biden and first lady Jill Biden had placed flowers at the same memorial on May 17 and had visited with the victims' families.

Biden is expected to head to Texas for a visit this weekend with the families of victims of Tuesday's school shooting.

Harris later told reporters the administration is not "sitting around waiting to figure out what the solution looks like" to the nation's gun violence problem.

"We know what works on that," she said, reiterating support for background checks and a ban on assault weapons.

"Let's have an assault weapons ban," she said. "An assault weapon is a weapon of war with no place, no place in civil society. Background checks: Why should anyone be able to buy a weapon that can kill other human beings without at least knowing: Hey, that person committed a violent crime before, are they a threat against themselves or others?"

Harris said the nation had to come together as well.

"We have to agree that if we are to be strong as a nation, we must stand strong, identifying our diversity as our unity," she said.

It has been a sad week of goodbyes for family and friends of the Buffalo shooting victims, a group that includes a restaurant worker who went to the market to buy his three-year-old's birthday cake; a father and die-hard Buffalo Bills fan who worked as a school bus aide; and a 32-year-old sister who moved to the city to help a brother battling leukaemia.

Authorities said 18-year-old Payton Gendron, who is white, targeted the store three hours from his home in Conklin because it is in a predominantly Black neighbourhood.

In all, 13 people were shot in the attack which federal authorities are investigating as a hate crime. Three people survived.

Gendron is charged with first-degree murder and is being held without bail. His attorney has entered a plea of not guilty on his behalf.

Australian Associated Press