Sydney siege: Channel 7 host Natalie Barr breaks down in tears realising she knew victim Katrina Dawson

An Australian TV presenter broke down in tears live on air while reading out the names of the Sydney siege victims, as she realised she knew one of them.

Channel 7 host Natalie Barr was overcome by emotion as she found out that Katrina Dawson, the sister of a friend of hers, had been killed in the attack at the Lindt Café in Martin Place, central Sydney.

"I'm just finding out ... that Katrina Dawson was the sister of a prominent barrister, Sandy Dawson, who has done some work for Channel Seven... Who I know and who I have friends who know," Barr said.

"[She was] a mother of three children ".

Dawson, 38, was killed as police stormed into the café where a gunman, identified as self-styled sheikh Man Haron Monis, had been holding 17 people captive for more than 16 hours.

Monis and another hostage, Tori Johnson, 34, were also killed.

Police have not confirmed whether the hostages were shot dead by the attacker or caught in crossfire.

According to some reports, Dawson was fatally wounded as she attempted to shield a pregnant friend from gunfire.

All staff at Channel 7 were closely touched by the incident that shocked Australia, as the broadcaster's officers are located just across the road from the Lindt café.