The governor of Maryland in the United States has declared a state of emergency in a community west of Baltimore hit by flash floods.

Raging water toppled buildings, swept away cars and rose as high as almost two metres in Ellicott City, about 22km west of Baltimore, on Sunday (local time).

The National Weather Service issued a flash flood warning for the city late in the afternoon, describing it as a “catastrophic and life-threatening” emergency.

An SOS flag hangs from a building during the flooding on Main Street of Ellicott City, Maryland. Photo: Twitter / Kali Harris

Maryland Governor Larry Hogan declared a state of emergency soon after.

“They say this is a once every 1000-year flood and we’ve had two of them in two years,” Mr Hogan said, referring to an earlier emergency in 2016.

Some residents of Ellicott City told The Baltimore Sun the flooding appeared to be worse than that storm two years ago that claimed two lives and destroyed local businesses.

The aftermath of the floods in Main Street Ellicott City. Photo: AAP

Governor Hogan announced on Facebook he was heading to the city.

Authorities had no immediate report of any injuries or fatalities though information was still preliminary.

Numerous water rescues were reported after heavy rain drenched the state and sent raging brown water surging down Main Street in Ellicott City and past vehicles.

Authorities said Ellicott City, on the west bank of Maryland’s Patapsco River, is prone to periodic flooding.

-with AAP