The gunman who slaughtered 49 people at a gay nightclub in Florida said he had a car rigged with bombs outside and threatened to strap hostages into explosive vests, according to partial transcripts of 911 calls he made released today.

Omar Mateen, 29, paused during a three-hour siege to telephone emergency dispatchers three times and to post internet messages from inside the Pulse nightclub professing his support for Islamist militant groups.

"You people are gonna get it, and I'm gonna ignite it if they try to do anything stupid," Mateen said during one of the 911 calls, according to a redacted transcript published by the Federal Bureau of Investigation.

Mateen told the emergency dispatcher he was wearing an explosive vest like the kind they "used in France," apparently referring to the deadly assault in Paris last November by Islamic militants, according to the transcript.

As victims were fleeing the club, they told police outside that the shooter said he was going to put four vests with bombs on victims within 15 minutes, the FBI said in its statement.

No such vests or improvised explosive devices were found in the nightclub or the suspect's car, however, the FBI said.

The gunman identified himself as an "Islamic soldier," according to the said, and he told a negotiator to tell America to stop bombing Syria and Iraq.

"When the crisis negotiator asked the shooter what he had done, the shooter stated, 'No, you already know what I did,'" the FBI transcript said.

The transcripts did not include a pledge of loyalty that authorities say he made to the Islamic State militant group. Authorities have said preliminary evidence indicates Mateen, who worked as a security guard, was a mentally disturbed individual who acted alone and without direction from outside networks.

Mateen, a New York-born U.S. citizen and Florida resident of Afghan descent, who has been described by U.S. officials as "self-radicalized" in his extremist sympathies.