WASHINGTON — At least five people have died in a winter storm that has seized a swathe of the US in its icy grip, leading to mass school closures, travel chaos and power cuts.

Seven US states declared emergencies: Maryland, Virginia, West Virginia, Kansas, Missouri, Kentucky and Arkansas.

More than 2,300 flights have been cancelled, with nearly 9,000 delays also reported owing to the extreme weather caused by the polar vortex of icy cold air that usually circles the North Pole.

Around 190,000 people had no power early on Tuesday across states in the storm's path, according to Poweroutage.us. Snow and sleet is forecast to continue through the day in much of the north-eastern US, according to the National Weather Service (NWS).

While the precipitation will then dissipate, cold Arctic air is expected to keep conditions icy across a chunk of the country for several more weeks.

In Washington DC, where lawmakers met on Monday to certify Donald Trump's win in November's election, about 5-9in (13-23cm) of snow fell, with up to a foot recorded in parts of nearby Maryland and Virginia.

In front of the Washington Monument, hundreds of local residents gathered at a local park for a snowball fight, a now 15-year-old tradition.

"Just having fun," one local man told the BBC. "Never done a snowball fight before."

Former US Olympic skier Clare Egan was found cross-country skiing on the National Mall, the central thoroughfare of the US capital city.

She told the Associated Press she had thought "my skiing days were maybe behind me", after moving to the city.

Washington DC's weather emergency is declared until the early hours of Tuesday as a result of the system, which was named Winter Storm Blair by the Weather Channel.

Children who had been due to go back to classes on Monday after the winter holiday break were instead enjoying a snow day as school districts closed from Maryland to Kansas.

In other parts of the US, the winter storm brought with it dangerous road conditions.

In Missouri, the state's highway patrol said at least 365 people had crashed on Sunday, leaving dozens injured and at least one dead.

In nearby Kansas, one of the worst-hit states, local news reported that two people were killed in a car crash during the storm.

In Houston, Texas, a person was found dead from cold weather in front of a bus stop on Monday morning, authorities said.

In Virginia, where 300 car crashes were reported between midnight and Monday morning, authorities warned local residents to avoid driving in large parts of the state.

At least one motorist was killed, according to local media reports.

Matthew Cappucci, a senior meteorologist at the weather app MyRadar, told the BBC that Kansas City had seen the heaviest snow in 32 years.

Some areas near the Ohio River turned to "skating rinks" in the frigid temperatures, he added.

"The ploughs are getting stuck, the police are getting stuck, everybody's getting stuck — stay home," he said. — BBC