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A senior Venezuelan finance official confirmed the deal but declined to give more details. Goldman didn’t negotiate the transaction with the government but instead bought the bonds through an unnamed broker, three of the people familiar with sale said.

But detractors said participating in any financial deals would give much-needed funding to the Maduro administration, which polls show has the support of only one in five Venezuelans. The government has shelved elections and is now organizing an overhaul of the constitution, which opposition leaders say will end the few constitutional protections Mr. Maduro’s political adversaries have.

“Goldman is putting itself on the wrong side of history with this deal,” said opposition lawmaker Angel Alvarado, who is a member of the Venezuelan congressional finance committee, calling it “a grave reputational error.”

“This is a bad decision not just from the ethical, but also from the business perspective,” he said. Mr. Alvarado added that an opposition-led administration, if it were to take power, would refrain from doing business with Goldman, whose asset management branch manages $1.3 trillion, of which about $40 billion is dedicated to emerging markets.

Venezuelan bonds are widely traded because of their hefty returns and Mr. Maduro’s relentless commitment to make good on debt obligations despite difficulties in paying for food imports.

The country’s debt securities also form a large portion of the bond indexes that major fixed-income funds measure their performance against. Venezuela has to pay $4.6 billion to service its debt for the remainder of the year.To make the payments, the cash-strapped government has had to resort to a series of ad hoc measures, including mortgaging Citgo Petroleum Corp., its U.S.-based oil refinery network.

Ricardo Hausmann, who is a former Venezuelan planning minister and a critic of the Maduro government, last week urged J.P. Morgan Chase & Co. to remove Venezuelan bonds from its benchmark emerging-market debt index. That would permit investors who trade entire asset classes to avoid holding debt issued by a government accused of rights abuses, the Harvard University economist said in an essay published on the website Project Syndicate.

The PdVSA 2022 bonds purchased by Goldman last week had until recently been in the possession of Venezuela’s central bank. The Central Bank of Venezuela’s international reserves jumped $442 million to $10.8 billion on Thursday, the day the bond deal was completed, according to official figures.