Tornadoes ripped through the US state of Alabama Monday, killing two, trapping many people in their homes, and leaving a trail of damage as well as tens of thousands without power.

"There has been significant home damage and power lines are down," Lieutenant Jeff Bridges with the town's police department told AFP.

Mike Calamura, 51, was still disoriented hours after a tornado tore off the roof of his Trussville home and knocked down most of his trees.

"I just had a mattress over my head. Completely over my head, and I was just praying," said Calamura, 51.

When he emerged he found the wind had sucked out one of doors of his two-car garage and had blown the other one in.

Nearby resident Rick Sutton gathered his valuables and fled to the basement with his wife and 22 year-old son when he heard the siren.

"The tornado was over in as short as 20 seconds," Sutton said. When he emerged he found his home was still standing, but the roof was gone and the windows were blown out. Trees were toppled on both his house and car.

And yet he was lucky -- about a dozen homes were leveled in a nearby neighborhood.

Governor Robert Bentley's office reported "tornados, severe thunderstorms, hail, and straight line winds" moving into the state. At least seven counties reported damage, he said as he declared a state of emergency.

"I urge Alabamians to heed weather warnings to protect their families, homes and businesses."

Chief Deputy Randy Christian with the Jefferson County Sheriff's Department told AFP a 16-year-old boy in the town of Clay and an 82-year-old man in Oak Grove, on the outskirts of Birmingham, were killed when tornados hit their homes.

"We are currently responding to reports of people trapped in their homes" in three other Birmingham locations, Christian said.

The state utility company said some 36,000 customers were without power across Alabama, the bulk in the Birmingham metropolitan area, population one million.

Schools in Jefferson County, where Birmingham is located, were closed for the day, while the Alabama Emergency Management Agency warned of severe storms, tornados and high winds across the state.

"First responders in affected areas are working hard," the AEMA said on its Twitter feed. "AEMA will assess damage when search/rescue complete."

Governor Bentley added that "the severe weather outbreak of last year is still fresh on our minds and is a reminder that we must take the threat of severe weather seriously."

Much of the region is still recovering from damage caused by severe weather on April 27, 2011, when some 240 tornados touched down in Alabama, killing more than 200 people and causing widespread destruction.

The death toll Monday may have been lower because more people took precautions: tornado sirens blared around 3:00 am, sending area residents scurrying into basements and safe areas.

Trussville resident Tyler Frederick, 10, said that the family dog alerted them of the tornado. "We're just glad that we survived," he said.