U.S. intelligence officials have authenticated at least 13 videos of the aftermath of an alleged Syrian gas attack showing men and children convulsing and struggling to breathe, a government official said Saturday.

The graphic videos, obtained by The Washington Post, have been made public previously on YouTube and other Internet sites. They are among as many as 100 public videos that purport to document victims of the Aug. 21 attack near Damascus.

The Central Intelligence Agency has confirmed these 13 videos as authentic, said the government official, who spoke on the condition of anonymity because of the sensitivity of the materials.

At the request of Sen. Dianne Feinstein (D-Calif.), chair of the Senate Intelligence Committee, the images were shown to senators on Thursday during a classified briefing that was part of congressional deliberations over whether to authorize President Obama to pursue limited military strikes against Syrian government targets.

A growing number of lawmakers on both sides of the aisle are objecting to such strikes, but administration officials and their congressional allies believe that the horrific scenes depicted in the videos could help sway public opinion. The administration has said at least 1,429 people, including 426 children, were killed in the alleged chemical attack.

EDITOR's NOTE: CONTAINS GRAPHIC CONTENT. This video was shown to Members of Congress in a classified briefing along with other footage on a DVD obtained by the Washington Post. (Youtube/SHAMSNN)

The videos, shot in several different locations, show shirtless men squirming and convulsing on the floor, as well as young boys and girls having difficulty breathing. In some cases, medics have placed oxygen masks over their mouths. Some show doctors looking into the glazed eyes of the victims, and in at least one case a man appears to be foaming at the mouth.

The CIA’s authentication of the 13 videos was first reported by CNN.

After the private Senate meeting Thursday, Feinstein told reporters: “I have asked the CIA to prepare a DVD which would have specific instances of evidence. . . . I saw it this morning and it was hideous.”

Later Saturday, Feinstein posted the videos to her Web site, with a disclaimer warning viewer discretion.

The videos were filmed by Syrians who support the rebel forces that have waged an extended campaign against Syrian President Bashar al-Assad’s authoritarian regime. The videos do not make clear who used the chemical weapons.

The Obama administration has said it has confirmed, through additional intelligence, including intercepted communications, witness accounts, photographs, news reports and other evidence, that the Assad regime is responsible.

As of Sept. 4, lawmakers appear to be tentatively dividing into four camps over military action in Syria.

A U.N. inspection team, which was in Syria on the day of the attack to investigate another reported incident, has gathered evidence on the Aug. 21 incident and is expected to present a report on its findings later this month. But that report will only make a determination of whether chemical agents were used — not of who is responsible.

In making the case for limited U.S. military strikes — which likely would involve cruise missile attacks on Syrian government targets, but no U.S. troops on the ground inside the country — Obama has repeatedly cited the deaths of the children to make an emotional appeal.

“I want people to understand that gassing innocent people, delivering chemical weapons against children, is not something we do,” Obama said during a news conference Friday in St. Petersburg, Russia, where he was attending an economic summit. “It’s prohibited in active wars between countries. We certainly don’t do it against kids. And we’ve got to stand up for that principle.”

Obama will deliver a nationally televised address Tuesday at the White House, and he will discuss the situation in interviews with six television networks on Monday.