The widow of a gunman who killed 49 people at an Orlando nightclub has been cleared of lying to the FBI and helping her husband in the terror attack.

Noor Salman began sobbing with joy when the decision was read out at the US district court in the Florida city.

She could have faced life in prison if found guilty of the two charges of obstructing justice and aiding husband Omar Mateen by providing material support to a terrorist organisation.

The verdict took three days of deliberation by the jury before they declared her not guilty of both counts.

Ms Salman was married to Mateen when he attacked gay nightspot Pulse in June 2016 as he claimed allegiance to Islamic State.

The court decision means no one has yet been held criminally responsible for the massacre and her acquittal is likely to be an emotional setback for the survivors and families of the victims.

Prosecutors argued Ms Salman knew about her husband's guns, his affinity for violent Muslim extremist videos and his intention to attack a location, but did nothing to stop him.

They also told the court that Ms Salman and Mateen scouted out potential targets together - including Disney World's shopping and entertainment complex - and she knew he was buying ammunition for his AR-15 in preparation for an attack.

She gave him a "green light to commit terrorism," prosecutors said.

Defence lawyers described Ms Salman as a simple woman with a low IQ who was abused by her husband. They told the court she didn't know of his plans because he concealed much of his life from her.

Attorney Charles Swift argued there was no way Ms Salman knew Mateen would attack the Pulse nightclub because even he didn't know he would attack it until moments before the shooting.

"It's a horrible, random, senseless killing by a monster," Mr Swift said during closing arguments. "But it wasn't preplanned. The importance to this case is that if he didn't know, she couldn't know."

Trial

During the trial, prosecutors said Ms Mateen, who was born in New York to Afghan immigrants, intended to attack Disney World's shopping and entertainment complex by hiding a gun in a stroller but became spooked by police and instead chose the gay club as his target.

Ms Salman's statement to the FBI in the hours after the attack appeared to play a key role in the case.

In the statement, Ms Salman said over "the last two years, Omar talked to me about jihad."

She claimed her husband didn't use the internet in their home, but he did. She also told

investigators that Mateen had deactivated his Facebook account in 2013, but they found that he had an account up until the month of the shooting - and was friends with his wife.

She said her husband only had one gun when he had three.

Investigators were told by her that Mateen wasn't radicalised, but it emerged he had pledged allegiance to the Islamic State group before he was killed.

Defense attorneys said the FBI coerced Salman's statement and she signed it because she was tired after extensive questioning and feared losing her young son. They fought to have it thrown out.

Jurors asked to review the statement more closely a couple of hours into their deliberations and the judge obliged, printing off copies for them.

Mateen was killed by police following the attack.

Ms Salman, was born in California to Palestinian parents. did not testify in her defence.