Nelson Martinez, the jailed former head of Venezuela's state-run oil giant PDVSA who was arrested last year as part of anti-corruption purge, died in state custody Wednesday, authorities said.

The chief prosecutor's office said Martinez suffered from a serious and chronic illness that led to his death at a medical facility where he was undergoing treatment.

The death is likely to focus attention on the conditions in which authorities are holding key opponents and former government officials. Martinez died two months after a Caracas councilman, Fernando Alban, fell to his death from a high-rise police building in what the government classifies a suicide but which the opposition insists was murder.

Martinez, who also served as oil minister, was arrested last year along with dozens of other executives and officials as part of an anti-corruption purge at PDVSA led by socialist President Nicolas Maduro.

At the time, Venezuela's top prosecutor said Martinez conspired with another former PDVSA president, Eulogio del Pino, to embezzle state funds through unauthorized financing deals by PDVSA's U.S. subsidiary, Citgo. Martinez headed the Houston-based Citgo between 2013 and 2017.

Rafael Ramirez, who was Martinez's boss before being pushed out himself as head of PDVSA, said his former colleague never wanted to assume leadership of the oil monopoly, knowing it would take a toll on his health after he underwent open heart surgery a few years back.

But Martinez was forced into taking the job by Maduro, Ramirez said in an interview, adding that he had personally informed the president of Martinez's heart problem.

"This death is Maduro's responsibility," said Ramirez, who angrily broke with the government last year amid accusations that he also was stealing from PDVSA. "The saddest thing is he didn't know why he was being held."

Corruption has long been rampant in Venezuela, which sits atop the world's largest petroleum reserves, but officials are rarely held accountable — a major irritant to citizens struggling to eat three meals a day amid widespread shortages and seven-digit inflation.

The U.S.-educated Martinez, an industry veteran, was replaced at PDVSA by an army general with no previous experience in the oil sector.

Ramirez said the government tries to keep its jailed political opponents safe for fear of sparking an international outcry. But he said the dozens arrested as part of the oil industry purge last year, including five former Citgo executives with U.S. passports, have mostly been forgotten and are seen unfairly as something less than political prisoners because they have been charged with corruption.

He said Martinez was being held in isolation at a military intelligence headquarters in Caracas and had been repeatedly denied visits from his family doctors, leading to depression that had worsened after he became sick with kidney problems a few weeks ago.

"It's as if the PDVSA prisoners don't exist," said Ramirez, who has been living in exile since resigning as Venezuela's ambassador to the United Nations last year.