Over five million people, including thousands of Indian-Americans, have been asked to evacuate from parts of coastal Florida after Hurricane Irma, an extremely powerful Category 5 storm, barrelled towards the state after wrecking havoc on the Caribbean islands.

Irma is expected to landfall in Florida on Sunday, which at its current trend officials said, is likely to cause devastation across Florida and surrounding areas.

Authorities in Florida have ordered 5.6 million people -- a quarter of the state's population -- to evacuate, warning that those who do not leave cannot expect rescue services to reach them once Irma hits.

"It is not a question of if Florida is going to be impacted, it is a question of how bad Florida's going to be impacted," said Brock Long, head of Federal Emergency Management Agency.

Hurricane Irma continues to be a threat that is going to devastate the United States, and either Florida or some of the southeastern states. This is a complex forecast. Anybody from Alabama to North Carolina should be watching this storm very closely, Long said.

Florida is also home to thousands of Indian-Americans.

In addition to thousands of federal employees, several thousand-military personals have been deployed by the Department of Defence to meet any eventuality in the aftermath of Irma hitting the coast of Florida.

"We need the people to listen to their local officials. But when we see evacuations taking place, what we try to do is break down the number that are going to need mass care support, and some of those numbers are well over 100,000 people in shelters for this event," Long said.

US President Donald Trump received a briefing on Hurricane Irma today. He "was given an overview of the recent impact of the hurricane on the US Virgin Islands, Puerto Rico, and neighbouring islands and the ongoing response efforts of the Federal and territorial governments," the White House said. A State of emergency has been declared in Florida.

Earlier in the day, Trump signed a legislation that provides an additional USD 15.25 billion in emergency appropriations for disaster relief and extends the authorisation of the National Flood Insurance Programme

through December 8.