Google's YouTube is in "fire drill" mode, according to a person close to the video service, The Wall Street Journal reported. YouTube is offering bonuses to some of the top video-makers to sign multiyear deals in which they agree to post content exclusively on YouTube for a time before putting it on a rival service.

Competitors Facebook and Vessel are trying to lure away the talent, the Journal said.

These YouTube personalities have huge online fan bases. YouTube gaming channel PewDiePie, has more than 32 million subscribers, for example, according to statistical website, SocialBlade.

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The Journal says YouTube executives are especially concerned with Vessel.

The video start-up's website, which is being built now, is backed financially by Benchmark, Greylock Partners and the personal investment company of Jeff Bezos. It was co-founded by former Hulu Chief Executive Jason Kilar and that company's former chief technology officer, Richard Tom.

Vessel has raised $75 million in venture capital, according to the Re/Code and is looking to secure programming ahead of a planned launch by the end of the year.

While the start-up might pose a threat, YouTube remains fiercely popular, 100 hours of video are uploaded to the service every minute and more than 6 billion hours of video are watched each month.

Disclosure: NBC News group is a minority stakeholder in Re/code and has a content sharing partnership with it.