Families of some of the 49 people killed in a massacre at an Orlando gay nightclub will mourn and bury their dead today, a day after President Barack Obama meets survivors and says the United States must act to control gun violence.

US investigators questions the wife of the gunman who killed 49 people at a gay nightclub in Orlando, the FBI say, and a law enforcement source says she could face criminal charges if there is evidence of any wrongdoing.

The wife of the gunman who killed 49 people at an Orlando gay nightclub could face criminal charges after a federal grand jury was convened to study possible wrongdoing by her, a law enforcement source says.

Wife of gunman who killed 49 people at an Orlando gay nightclub knew of his plans for the attack and could soon be charged in connection with the deadliest mass shooting in modern US history, a law enforcement source said on Tuesday.

A survivor of the Orlando attack who was shot three times has described playing dead while Omar Mateen fired relentlessly at people on the floor.