6pm. Prime Minister Julia Gillard says authorities are not aware of any Australian victims of the United States tornado.
"I express my condolences and sympathy to the families of those killed and injured in the Oklahoma tornado," Ms Gillard said in a statement.
4pm: The death toll from a massive tornado that swept through a US suburb of Oklahoma City has risen to 91, including at least 20 children, an official told CNN.
At least 145 people were injured including 70 children, hospitals reported.
3pm: The state medical examiner's office released the latest death toll at 51, as emergency crews combed through smashed homes and the collapsed remains of an elementary school in Moore, Oklahoma.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
At least 20 of those killed were children, the examiner says.
Stunned weather forecasters reported a two-mile (three-kilometre) wide swathe of vicious winds and television news helicopters tracked a dark and deadly funnel plowing through densely-packed suburbs.
11.30am: More images from Moore, Oklahoma, after it was hit by a deadly tornado:
11.10am: Storm chaser Chris McBee tells SBS this was the worst tornado he's ever seen in terms of magnitude and destruction.
"In fact, I'm hearing that this may be one of the worst tornadoes in history," he says. "This is above and beyond anything I've ever seen." Read more.
11.03am: The state medical examiner's office says 51 people have been killed.
10.53am: Oklahoma Governor Mary Fallin is giving a press conference right now, thanking first responders and assuring those who may be stuck or left homeless that they'll have resources sent out to them as soon as possible.
10.45am: Before and after pictures of the Moore Medical Center:
10.35am: This screenshot is taken from a live report from the carpark of what used to be Moore Medical Center. Rescue and emergency services have been searching cars in the lot for bodies, and marking them with a red 'X' once they have been checked.
10.18am: The state medical examiner's office has revised the death toll to 37. This number is expected to rise.
Local authorities are expected to hold a major press conference shortly.
10.15am: As sunset approaches in Oklahoma, it looks like rescue crews are preparing to work through the night at the Plaza Towers school, with a number of portable light generators being brought to the scene.
9.59am: The bodies of seven children have been found at Plaza Towers Elementary School, according to local media reports. Lance West from KFOR TV News is at the scene, and says the children were discovered in a pool of water, having drowned.
"There don't appear to be any more survivors in that school," he said.
While it's unclear how many people remain trapped in the rubble, emergency services estimate the number could be between 20 and 30.
Earlier, the Oklahoma City medical examiner's office confirmed ten deaths as a result of the tornado.
9.46am: Google has released a crisis map of the storm over Oklahoma:
