Dozens killed in Oklahoma tornado

At least 91 people, including 20 children, have been left dead after a huge tornado tore through Oklahoma City suburbs, officials in the US state say.

Worst hit was Moore, south of the city, where neighbourhoods were flattened and schools destroyed by winds of up to 200mph (320km/h).

About 120 people are being treated in hospitals.

President Barack Obama has declared a major disaster in Oklahoma.

He also ordered the federal authorities to join in the search and recovery efforts which are continuing throughout the night.

Monday's twister hit Moore, a suburb of about 55,000 people, and remained on the ground for about 45 minutes.

The Oklahoma chief medical examiner's office said at least 20 children were among the 91 dead.

Plaza Towers Elementary school took a direct hit: the storm tore off the building's roof and knocked down walls.

"The school was flattened. The walls were pancaked in," Oklahoma's Lt Gov Todd Lamb told the BBC.

"There's still roughly two dozen children that are missing. There have been some bodies recovered from that school and it's absolutely horrific and devastating."

Another school - Briarwood Elementary - was also damaged, and teachers were later seen leading pupils out to safety.

Oklahoma Gov Mary Fallin said it was a "tragic" day.

More than 200 Oklahoma National Guardsmen as well as out-of-state personnel have been called in to assist the search-and-rescue effort.

'Most powerful tornado'

Shocked survivors spoke of the tornado's power.

"We locked the cellar door once we saw it coming, it got louder and next thing you know is you see the latch coming undone," survivor Ricky Stover said.

"We couldn't reach for it and it ripped open the door and just glass and debris started slamming on us and we thought we were dead, to be honest."

Melissa Newton said: "There's shingles and pieces of sheet rock and wood in our yard and all across our neighbourhood. Some homes are completely gone. It's devastating."

-BBC