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 released on Monday.

Omar Mateen, 29, paused during a three-hour siege to phone emergency dispatchers three times and to post online 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 FBI.

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

The transcripts did not include a pledge of loyalty that authorities say he made to the Islamic State militant group.

The Pulse massacre has triggered a new effort to break a long-standing stalemate in Congress over gun control.

The Senate was set to vote Monday on four competing measures from both parties to expand background checks on gun buyers and to curb gun sales to people on terrorism watch lists. Donald Trump, the presumptive Republican presidential nominee who fired campaign manager Corey ­Lewandowski on Monday, has said he shares the goal of keeping guns out of the hands of people on watch lists.