Orlando transcripts of three phone calls to be released

Omar Mateen. Photo / AP

US officials are planning to release partial transcripts of three phone conversations the Orlando gunman had with police as the massacre, in which he killed 49 people in a Florida gay nightclub, unfolded.

Attorney General Loretta Lynch told CNN the Orlando shooting incident was "an act of terror and an act of hate", but she declined to say what charges may be filed nor who may be charged in the case.

The transcripts of the conversations, due to be released tomorrow NZT, are between deceased gunman Omar Mateen and law enforcement negotiators.

They will "talk about what he told law enforcement on the ground as the events were unfolding", Lynch said.

"As we have said earlier, he talked about his pledges of allegiance to a terrorist group. "He talked about his motivations for why he was claiming at that time he was committing his horrific act," the Attorney General said.

Lynch said, however, that the transcripts would be edited to "avoid revictimising those who went through this horror, but it will contain the substance of his conversations."

She told the ABC the transcripts would not include his pledge of allegiance to Isis (Islamic State). Lynch also said she would travel to Orlando on Wednesday to confer with investigators and meet survivors of the worst domestic shooting incident in American history.

She declined to say whether a federal grand jury was likely to charge Mateen's second wife, Noor Salman.

US officials have said Salman knew of her husband's plans to carry out the attack.

"Because this investigation is open and ongoing, we're not commenting on anyone else's role in it right now, except to say that we are talking to everyone who knew him, and that of course includes his family, to determine what they knew, what they saw in the days and weeks leading up to this," Lynch said.

- Reuters, AAP