Washington (AFP) – US prisoners on Tuesday declared a nationwide strike demanding changes to correctional institutions including living conditions, pathways to parole and voting rights restoration.

The US incarceration rate is the world’s highest: about 2.2 million people were behind bars at the end of 2016, a figure the American Civil Liberties Union says represents approximately one-fifth of the global population of prisoners.

The strike — set to continue through September 9, according to organizers — was called in response to a deadly riot in April at a maximum security prison in South Carolina, Lee Correctional Institution.

“Seven comrades lost their lives during a senseless uprising that could have been avoided had the prison not been so overcrowded from the greed wrought by mass incarceration, and a lack of respect for human life that is embedded in our nation’s penal ideology,” the group of incarcerated prison rights advocates leading the strike said.

“These men and women are demanding humane living conditions, access to rehabilitation, sentencing reform and the end of modern day slavery,” the group, known as Jailhouse Lawyers Speak, said in a statement.

Organizers throughout the United States advised inmates to engage in peaceful sit-ins, hunger strikes and work stoppages.

Low remuneration for prisoners put to work at jobs like cooking and cleaning is high on the list of grievances released by organizers, who dubbed the practice “slavery.”

Udi Ofer, who leads the ACLU Campaign for Smart Justice, praised the strikers and backed their 10 demands, particularly the right to vote for felons and prisoners.

Felon enfranchisement laws vary state by state, but in many places inmates lose voting rights for a period while incarcerated, and sometimes after release as well.

“Our country is stronger when people most marginalized and directly impacted by unjust policies raise their voices in protest and demand a different future,” Ofer said in a statement. “The courageous people who are bringing focused attention to America’s system of mass incarceration through the Nationwide Prison Strike deserve our admiration.”

“We urge corrections officials not to respond with retaliation,” he added.

“Peaceful demonstrations challenging unjust conditions and practices do not merit placing participants into solitary confinement or adding time to their sentences.”

In 2016, inmates responded to a similar call to action, with prisoners striking in states including Florida, Alabama, Texas and South Carolina.