CARACAS, Venezuela (AFP) — A Venezuelan man arrested in protests that erupted after President Nicolas Maduro claimed a disputed election victory has died in prison, an NGO and his son said.

It was the second such fatality among the several thousand people detained after the July 28 election as outraged citizens took to the streets to cry foul and insist the opposition had won.

Jesus Rafael Alvarez, 44, died last Thursday in a maximum security prison in the central city of Carabobo, according to an NGO called the Venezuelan Prison Observatory.

“They punished my father and killed him in prison,” his 22-year-old son, also named Jesus, said in a statement issued by the NGO.

He told AFP he learned of his father’s death on social media and went to the morgue, but was not allowed to see the body nor told the cause of death.

“All they showed me of his were some belongings and some photos,” Alvarez said.

In the photos, the older Alvarez is emaciated and unrecognisable, with signs of a beating, the NGO said.

A total of 27 people died in post-election clashes between demonstrators and security forces and nearly 200 were wounded.

The other prisoner to die after being arrested in the protests was Jesus Manuel Martinez, 36, a member of the opposition party led by Maria Corina Machado.

He died in a hospital from heart trouble associated with diabetes.

More than 2,400 people were arrested in the protests that broke out after Maduro claimed victory for a third six-year term.

Maduro has overseen the oil-rich country’s decline into economic ruin and been accused of acting like a brutal leftist dictator.

The government says it has freed more than 300 of these detainees. But an NGO called Foro Penal, which advocates for political prisoners, said its tally is lower, at 208, including some minors.