The parents of Hersh Goldberg-Polin, who was taken hostage by Hamas more than six months ago, felt a "total mix of emotions" when a new video of their son was released on Wednesday.

"First and foremost, just a huge sense of relief and gratitude to both see him and hear him. Something about that multi-sensory was really overwhelming. He's alive," Jon Polin, his father, said in an interview on "Good Morning America" on Thursday. "Assuming this video is current, which we believe it is, he's alive."

A video released on Wednesday on a Hamas-run Telegram channel showed a man who identified himself as Goldberg-Polin, a 24-year-old American who was captured at the Nova Music Festival on Oct. 7.

In the heavily edited video, the Israeli-American hostage asks Israeli Prime Minister Benjamin Netanyahu and his government to continue working to secure the release of the hostages.

Rachel Goldberg, his mother, said on Thursday she couldn't pay attention to the words her son was saying when she first watched the new video.

"I wasn't even listening to the content, I was just hearing my only son's voice. Seeing him move and try to look into his eyes," she said. "Any parent, anyone, anyone who has parents, can imagine after 201 days, more than half a year of doubt and fear and angst and trauma to have that, it was very bittersweet. And it was truly overwhelming."

Goldberg-Polin's parents in a "GMA" interview in October described their son as a "curious" and a "laid-back person."

Goldberg said at the time that her mantra had become, "Stay strong, survive. Stay strong, survive."

She repeated that mantra on Thursday.

"We love you, stay strong, survive," she said. "And I definitely, you know, more than ever, after seeing him and seeing that he is clearly medically compromised, medically fragile, that is my continued plea to him, to his soul."

-ABC News' Kevin Shalvey

A video showing a man who identifies himself as Hersh Goldberg-Polin, a 24-year-old American who was captured at the Nova Music Festival on Oct. 7, and made under duress, was released Wednesday on a Hamas-run Telegram channel.

According to the video, his left arm has been amputated at the forearm. Goldberg-Polin suffered a serious injury to that arm before being captured, his parents told ABC News in an interview in Israel just days after the attack. His family said Wednesday they wanted the video and its message published.

In the heavily edited video made under duress, he denounces Israeli Prime Minister Benjamin Netanyahu for failing to secure the release of the hostages.

It is unclear when the video was filmed. In the video, he makes reference to a holiday and says he has been held for nearly 200 days.

"Hirsch's cry is the cry of all the abductees - their time is up! The State of Israel has no more time to waste, the abductees must be put first, without them the State of Israel will have no resurrection and no victory. All must be brought home - the living for rehabilitation, the murdered for a dignified burial," a spokesperson for the Hostage Release Center said in a statement Wednesday.

This post has been updated.

The World Food Programme warns that famine in the Gaza Strip is getting closer by the day and it could surpass famine thresholds of food insecurity, malnutrition and mortality in six weeks, according to an official.

"We estimate 30% of children below age of two is now acutely malnourished or wasted, and 70% of the population in the north is facing catastrophic hunger. There is reasonable evidence that all three famine thresholds -- food insecurity, malnutrition, mortality -- will be passed in the next six weeks," said Gian Carlo Cirri, the director of the World Food Programme's Geneva office.

"The conflict makes it so difficult and sometimes impossible to reach affected people that as humanitarians we usually don't -- for humanitarian principles, to abide to those principles -- we don't call for ceasefire. On these two contexts, we have no other choice than asking for a ceasefire. This is the only way for us as humanitarians, as World Food Programme, to access these people that are in acute needs."

-ABC News' Will Gretsky

More than 310 aid trucks entered Gaza Tuesday, the highest number of aid vehicles that have entered Gaza since the Israel-Hamas conflict began, according to the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA).

"It needs now to be sustained & further increased," the agency said in a statement.

The UNRWA, which has been critical of the aid effort in Gaza, reiterated its calls for increased access for humanitarian groups to prevent famine in the region.

-ABC News' Will Gretsky