Baku, May 21 (AZERTAC). A massive tornado at least a half mile-wide with 200 mph winds churned through Oklahoma City's suburbs Monday afternoon, killing at least 51 people including at least 20 children, flattening entire neighbourhoods and destroying an elementary school with a direct blow as children and teachers huddled inside.

Amy Elliott, a spokeswoman for the Oklahoma Medical Examiner's Office, said at least 51 people were killed and the death toll is expected to rise. At least twenty of dead were children, Elliot said.

The storm laid waste to scores of buildings in Moore, a community of 41,000 people about 10 miles south of Oklahoma City. Block after block lay in ruins. Homes were crushed into piles of broken wood. Cars and trucks were left crumpled on the roadside.

More than 120 people were being treated at hospitals, including about 50 children.

Search and rescue crews were looking for anyone who may be trapped in the rubble. Many land lines to stricken areas were down, and cell phone networks were congested. The storm was so massive that it will take time to establish communications between rescuers and state officials, Oklahoma Gov. Mary Fallin said.

Fallin deployed 80 National Guard members to assist with rescue operations and activated extra highway patrol officers. She also spoke with President B. Obama, who declared a major disaster and ordered federal aid to supplement state and local recovery efforts.

James Rushing, who lives across the street from the school, heard reports of the approaching twister and ran to the school, where his 5-year-old foster son, Aiden, attends classes. Rushing believed he would be safer there.

"About two minutes after I got there, the school started coming apart," he said.

The students were sent into the restroom.

As dusk began to fall, heavy equipment was rolled up to the school, and emergency workers wearing yellow crawled among the ruins, searching for survivors.

Because the ground was muddy, bulldozers and front-end loaders were getting stuck. Crews used jackhammers and sledgehammers to tear away concrete, and chunks were being thrown to the side as the workers dug.

OU Medical Centre spokesman Scott Coppenbarger said the hospital and a nearby children's hospital are treating approximately 85 patients, including 65 children, with conditions ranging from minor injuries to critical.