Chinese Islamic leaders at a symposium held to reinforce a positive image of Islam and curb extremism condemned the deadly mass shooting at an LGBT venue in downtown Orlando, Florida, in the United States.

"We condemn this attack on innocent civilians. It is an act of terror against humanity and has nothing to do with religious factors," Adiljan Haji Kerim, vice-president of the Islamic Association of China, said on the sidelines of the symposium.

The mass shooting, the worst in US history, took place on Sunday as a man armed with an assault rifle killed 50 people at a packed gay nightclub in Orlando, Florida. Police killed the shooter, who was identified as Omar Mateen, 29, a US citizen who was the son of immigrants from Afghanistan.