U.S. President Barack Obama on Sunday called on Americans to help rebuild the tornado-ravaged Oklahoma City area during a visit to places worst hit by the deadly twister on Monday afternoon.

U.S. President Barack Obama on Sunday called on Americans to help rebuild the tornado-ravaged Oklahoma City area during a visit to places worst hit by the deadly twister on Monday afternoon.

Obama toured some of the hardest-hit areas and meeting with officials and residents in the Oklahoma City suburb of Moore on Sunday afternoon, according to local media reports.

The tornado, classified as an EF-5 or the strongest storm on Earth with 200 mph-plus winds, killed 24 people and injured 377 others. As many as 12,000 homes were damaged. Official statistics estimated the damage caused by the tornado at $2 billion.

"It's going to take a long time for this community to rebuild, so I want to urge every American to step up," Obama said, urging Americans to help the storm relief and reconstruction efforts and to donate via the American Red Cross website.

Oklahoma Governor Mary Fallin said on Sunday that the state needs quick action from the Federal Emergency Management Agency ( FEMA) to help Moore, a town of some 41,000 people.

The White House said that FEMA has already provided 57 million U.S. dollars in rebates and incentives to help build about 12,000 storm shelters in Oklahoma, according to earlier reports.