UNITED NATIONS (AFP) - United Nations chief Ban Ki Moon on Tuesday offered the global body's help to the state of Oklahoma in the United States, struck by a brutal tornado that killed at least two dozen people.

"The secretary general has written to the governor of Oklahoma, Ms Mary Fallin, to express his solidarity and to offer the assistance of the United Nations, if requested, to help with the recovery efforts," said deputy spokesman Eduardo del Buey.

Mr Ban "sends his deepest condolences to those who have lost loved ones and to everyone affected by the storm," he said.

The giant twister tore through the outskirts of Oklahoma City on Monday afternoon, causing chaos as it plowed over homes, schools and other buildings in its path.

Authorities say 24 people are confirmed dead, including nine children.