The tapes also show al Qaeda operatives apparently practicing ambushes and kidnapping. Most of the tapes appear to be made before Sept. 11, although some show recorded television coverage of last fall's attacks in New York and Washington.
CNN said its correspondent, Nic Robertson, acquired more than 250 tapes through a longtime source, and he drove 17 hours from Kabul to a remote part of Afghanistan to first see them. CNN did not pay for the tapes, Robertson said.
The network said it showed the tapes to several experts to verify their authenticity.
The New York Times, which was shown portions of the tapes last week, quoted an expert who viewed the tapes as saying the tapes suggest Western intelligence agencies may be underestimating al Qaeda.
"In conjunction with the Encyclopedia of Jihad and other written manuals, the tapes show meticulous planning, preparation and attention to the tradecraft of terror," said Marcus Ranstorp, director-designate of the Center for the Study of Terrorism and Political Violence at the University of St. Andrews in Scotland.
A CNN spokeswoman declined to say more about how the tapes were obtained, and said it did not believe the network was being used in any way by Osama bin Laden's network to get a message across.
"Obviously, we're always mindful of not airing propaganda," Christa Robinson said. "Clearly, this is newsworthy."
White House spokesman Scott Stanzel declined comment on the tapes Sunday night.
CNN plans to reveal the tapes' contents through several reports this week, and show the poison gas experiments Monday. Sunday's report showed repeated images of a white dog locked in a cloudy, glass box.
The Times reported in Monday editions that in the videotape, a man drops something on the floor of a room where the dog is and a liquid spills across the floor and a vapor fills the room.
The tapes show several images of the dog vomiting and moaning, the Times reported. Ultimately, one of the dog's hind legs shoots up in the air, as its head goes down. The dog is then motionless.
It's not clear how much of this sequence CNN will air. "None of it, we can tell you, will be easy to watch," CNN anchor Aaron Brown said Sunday. "Some of it sickened us."
The ability of terrorists to unleash poisons was known even before the Sept. 11 attacks last year, when a convicted terrorist collaborator, Ahmed Ressam, testified about the experiments in the trial of a man accused of conspiring with him to bomb the Los Angeles airport.
CNN showed images of masked terrorists intercepting a vehicle along a dusty road in apparent training for a kidnapping. They also showed bin Laden, surrounded by tight security.
The tapes also show images of bin Laden being interviewed by journalists, Robertson said, indicating they were from a private library of al Qaeda material made to document their work.
CNN, on its Web site, said it had shown the material to terrorism expert Rohan Gunaratna, author of "Inside Al Qaeda." Gunaratna told the network he had not seen these tapes before and believes they were intended only for the terror group's leaders to see.