Actor and activist George Takei is weighing in on the treatment of undocumented immigrants and backing Rep. Alexandria Ocasio-Cortez's description of migrant detention centers as concentration camps. "I know what concentration camps are. I was inside two of them, in America. And yes, we are operating such camps again," Takei wrote on Twitter Tuesday.

Takei's tweet comes after Ocasio-Cortez said in an Instagram live video that "The United States is running concentration camps on our southern border and that is exactly what they are."

I know what concentration camps are. I was inside two of them, in America. And yes, we are operating such camps again. — George Takei (@GeorgeTakei) June 19, 2019

Takei, who rose to fame in "Star Trek" and became a gay rights activist, spent part of his childhood held with his family at the Rohwer Relocation Center in Arkansas, an internment camp for Japanese-Americans during World War II.

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In an interview with the Television Academy, Takei opened up about life in the camp. "Childhood is amazing adaptable. By the time we went to the Rohwer camp in Arkansas, I was 5 years old," he remembered. "The barbed wire fence, the guard tower ... the machine guns, they became a normal part of my landscape."

"I learned recite the Pledge of Allegiance to the flag with the sight of a high guard tower and machine guns pointing at us," he said. "I was too young to appreciate the irony as I recited the words, 'With liberty and justice for all.'"

In 2013, Takei traveled back to Rohwer with CBS News' Michelle Miler. "We were all concentrated, densely concentrated," he said. "We happened to look like the people that bombed Pearl Harbor, and put in prison camps simply because of our race."

He recalled how his family was forced out of their home at gunpoint and moved into their new "home" at Rohwer, which was a small, single room in a tar-paper barrack. Records at the National Archives show Takei, born Hosato G. Takei, and his family were transferred to the Rohwer camp after being held at the Santa Anita Assembly Center in California.

The Trump administration announced earlier this month that another site used as an internment camp during WWII, Fort Sill in Oklahoma, will be adapted to shelter migrant children. Shortly after, Ocasio-Cortez went live on Instagram to share her concern and outrage about the detention centers.

She recently doubled down on calling the centers "concentration camps," tweeting on Wednesday: "We are calling these camps what they are because they fit squarely in an academic consensus and definition. History will be kind to those who stood up to this injustice. So say what you will. Kids are dying and I'm not here to make people feel comfortable about that."

We are calling these camps what they are because they fit squarely in an academic consensus and definition. History will be kind to those who stood up to this injustice. So say what you will. Kids are dying and I’m not here to make people feel comfortable about that. — Alexandria Ocasio-Cortez (@AOC) June 19, 2019

The controversial comments were ill received by many, with critics saying evoking the Holocaust was not an appropriate comparison.

"Please @AOC do us all a favor and spend just a few minutes learning some actual history. 6 million Jews were exterminated in the Holocaust. You demean their memory and disgrace yourself with comments like this," Republican Rep. Liz Cheney, the daughter of former Vice President Dick Cheney, tweeted.

"@AOC needs to stop trying to draw these crayon parallels between POTUS & Hitler!" Republican Rep. Lee Zeldin, who is Jewish, tweeted.

And Republican Senator Lindsey Graham tweeted, "comparing the men and women serving our country to concentration camp guards do the Congress and country a great disservice."

Please @AOC do us all a favor and spend just a few minutes learning some actual history. 6 million Jews were exterminated in the Holocaust. You demean their memory and disgrace yourself with comments like this. https://t.co/NX5KPPb2Hl — Liz Cheney (@Liz_Cheney) June 18, 2019

.@AOC needs to stop trying to draw these crayon parallels between POTUS & Hitler! Try working WITH your colleagues on BOTH sides of the aisle to secure our border & fix this rather than desperately trying to promote mass hysteria w this disgusting & woefully false comparison. https://t.co/2X2dZvjVQa — Lee Zeldin (@RepLeeZeldin) June 18, 2019