JOHANNESBURG — China pledged $60 billion in development assistance to Africa on Friday, promising to help nations industrialize and elevate its relationship with the continent beyond one centered on the extraction of raw materials.

Speaking before most of the continent’s leaders at a China-Africa summit meeting here, President Xi Jinping tripled the amount pledged at the last meeting three years ago, reassuring the audience of China’s commitment amid an economic downturn whose effects have reverberated across Africa this year.

Against longstanding accusations that China benefits from a lopsided relationship with Africa, contentions that have recently gained traction as China’s trade deficits with many African nations have widened, Mr. Xi said that “China has the strong political commitment to supporting Africa in achieving development and prosperity.”

China, he said, “now has the technology, equipment, professional and skilled personnel and capital needed to help Africa realize sustainable self-development.” Mr. Xi pledged many of these things as part of the $60 billion package, which includes $5 billion in grants and interest-free loans and $35 billion in loans and export credits.