Orlando nightclub shooter Omar Mateen was taunted for being Muslim

Orlando gay nightclub shooter Omar Mateen, who killed 49 people in an attack last month, was subjected to taunting at his work place for being a Muslim, documents said.

While working as a security guard at the St Lucie county courthouse, Mateen was called "evil", a "towel head" and a member of a "blood sucking cult" by fellow security guards, International Business Times reported.

In one such incident, a security guard said: "We need to kill all Muslims."

The records, released on Monday, revealed that Mateen, 29, had complained of being the victim of physical intimidation as well as religious and ethnic taunts, the Orlando Sentinel reported.

Mateen used the complaint to accuse both employees at G4S, a private contractor that provided security guards, and St Lucie county deputies of harassment.

He was called "a f*****g terrorist" and "a camel jockey" by his employees, the documents said.

Monica Lewman-Garcia, a spokeswoman for G4S, confirmed that Mateen had filed a workplace-harassment complaint.

The allegations, released by the St Lucie county sheriff's office, were part of a five-page complaint Mateen filed in 2013, after he was questioned by the FBI.

Federal investigators were looking into on the job claims Mateen had made about having ties to the Boston Marathon bomber and the Fort Hood shooter.

However, Mateen said those claims were his attempt to get his colleagues to stop harassing him.

"I love the US," he wrote. "I'm 1000% pure American. I'm ready to give up my life defending the US."

Mateen was interviewed twice, once on September 26, 2013, and again a month later by FBI agents. Investigators concluded Mateen was not a terrorist, removed him from the list and ended the probe.

Officials said Mateen was radicalised before his attack on the Pulse nightclub on June 12, but there was no evidence that he was directed by a foreign terrorist group.