Bill Clinton accuses #BlackLivesMatter rally protesters of defending 'gang leaders'
Former President Bill Clinton clashes with protesters during a rally for his wife Hillary's presidential campaign on April 7, 2016. (YouTube)

Bill Clinton angrily told Black Lives Matter protesters that they "are defending the people who kill the lives you say matter," prompting criticism from black voters whose support Hillary Clinton is counting on in her quest for the presidency.

The former president spent more than 10 minutes facing down the protesters at a campaign rally in Philadelphia for his wife over the criticisms that a 1994 crime bill he approved while president led to a surge in the imprisonment of black people.

The Democratic race has become increasingly heated in recent days as Hillary Clinton, stung by a string of losses in state nominating contests, has traded barbs with her rival for the nomination, Bernie Sanders, over who is more prepared for the White House.

In Philadelphia, several protesters heckled the former president mid-speech and held signs, including one that read "CLINTON Crime Bill Destroyed Our Communities."

Video footage of Hillary Clinton defending the bill in 1994 by calling young people in gangs "super predators" who need to "be brought to heel" have been widely circulated during the campaign by activists in the Black Lives Matter protest movement.

Bill Clinton defended her 1994 remarks, which protesters say were racially insensitive.

"I don't know how you would characterize the gang leaders who got 13-year-old kids hopped on crack and sent them out on the street to murder other African-American children," he said, shaking his finger at a heckler as Clinton supporters cheered, according to video of the event. "Maybe you thought they were good citizens. She (Hillary Clinton) didn't."

"You are defending the people who kill the lives you say matter," he told a protester. "Tell the truth."

Hillary Clinton, who also has faced protesters upset by her remarks, has said she regrets using the term.

Bill Clinton said last year that he regrets signing the Violent Crime Control and Law Enforcement Act into law because it contributed to the country's high incarceration rate of black people for nonviolent crimes.

His remarks on Thursday prompted criticism online as some saw him criticizing the Black Lives Matter movement, which was the product of anger over a string of encounters around the country in which police officers killed unarmed black people.

Johnetta Elzie, a prominent civil-rights activist, wrote online that Clinton "can't handle being confronted by his own record."

"This is like watching a robot malfunction," she wrote.

Earlier in Philadelphia, Sanders, a U.S. senator from Vermont, doubled down on his criticism that Clinton is unqualified to be president as the two campaigns became increasingly testy less than two weeks before New York's election contest.

"Are you qualified to be president of the United States when you're raising millions of dollars from Wall Street, an entity whose greed, recklessness and illegal behavior helped destroy our economy?" Sanders said at a news conference.

Clinton this week sharply questioned Sanders' credentials and ability to carry out a campaign pledge to break up the big banks.

Spokesmen for Clinton noted that she never said the word "unqualified" when she questioned his preparedness for the presidency, but they declined to say whether she believes in that characterization.

Clinton aimed for a more magnanimous tone than her aides when speaking to reporters during a subway ride in New York City.

"I don't know why he's saying that," she said of Sanders' calling her unqualified, "but I will take Bernie Sanders over Ted Cruz or Donald Trump any time."

(Reporting by Luciana Lopez and Jonathan Allen; Additional reporting by Doina Chiacu, Megan Cassella, Alana Wise and Amanda Becker in Washington; Editing by Jonathan Oatis and Grant McCool)

Watch footage from the rally, as posted online, below.