Media playback is unsupported on your device Media caption Videos from Tepco's Fukushima nuclear plant show managers and workers struggling with the accident after the 2011 tsunami critically damaged its reactors

Tokyo Electric Power Company (Tepco), owner of the crippled Fukushima nuclear plant, has released footage of how it managed meltdowns in three reactors.

In the footage, workers can be seen dealing with what they thought was an explosion and urgently trying to understand the scale of the problem.

Tepco has faced criticism over the way it handled the nuclear crisis.

Analysis Tepco has bowed to pressure to release 150 hours of teleconferencing footage but the tape was heavily edited and mostly muted to "protect employees' privacy". So you could see the back of former PM Naoto Kan, who appeared angry in the tape, but you could not hear him as only one third of the released footage was audible. The other parts showed workers' frustration with Mr Kan as well as the then plant manager of the Fukushima Daiichi power plant, Masao Yoshida, asking his management to stop asking him so many questions and not to disturb him. Tepco is again under criticism for not releasing the full recordings and has been asked if it was removing more than employees' names and phone numbers.

Last year's meltdown, caused by an earthquake and tsunami, was the world's worst nuclear crisis since Chernobyl.

It led to the mass evacuation of some 160,000 people and has rendered parts of the surrounding countryside uninhabitable.

Tepco initially refused to release the films, but has done so after a change in management.

'Serious'

In the video, Tepco officials are heard urgently calling their headquarters.

"This is serious. This is serious," the video shows plant manager Masao Yoshida saying.

It is part of more than 150 hours of video recorded between 11 March, the day the tsunami hit, and 16 March.

However, while Tepco has released some of the audio and pictures of what happened, large portions of the video are without sound.

Tepco says some parts were edited to conceal the identity of some employees. Faces and names of employees are blurred in sections of the tapes.

The prime minister at the time, Naoto Kan, is also seen rushing into Tepco headquarters, but that part of the tape does not have audio.