Video footage of a Croatian television presenter fainting live on air while discussing the importance of oxygen has gone viral online.

Zlata Muck collapsed during the broadcast of educational children's programme Školski Sat (School Hour) earlier this week.

In the 30-second clip posted on YouTube, she can be seen introducing the topic of the day before passing out.

"Good morning and welcome to School Hour," Muck tells the young viewers. "Today, the first 35 minutes of our show will be dedicated to one of the most important elements on Earth: oxygen. Without it there..."

Her voice suddenly trails off and she staggers backwards before losing consciousness and hitting her head on the set behind her. She was not seriously injured.

As producers rush to her aid the show cut to an archive programme.

Muck managed to make light of the incident and closed the show joking: "Well, now we all saw what happens when you don't get enough oxygen".

One amused viewer wrote said: "The irony is, she was talking about the importance of oxygen."

Another wrote: "What happened maybe she's too much stress and really tired omg..."

According to local media, Muck is three months pregnant. She was reportedly taken to hospital as a precaution.