According to National Rail, only one exit was functioning at King's Cross as police addressed "an incident" outside.
Among those present at the station was Chris Woodhouse, who said families were in tears on the platforms as trains bound for airports were among those cancelled because of the demonstration.
All lines in an out of the station have been suspended as a result of the demo, which began around 1pm.
King's Cross in London has been closed today because of a pro-Kurdish demonstration at the station. "Therefore, train services may be revised and diverted".
Rail passengers faced hours of disruption after protesters on the tracks brought services to a standstill at one of the country's busiest stations..
Red flags displaying the emblem of the proscribed PKK are also visible in images of the Manchester Piccadilly protest posted to social media.
Trump pushes back on report he's 'unhappy' with legal team
Maggie Haberman, the New York Times White House correspondent who co-wrote the story with Michael Schmidt, immediately responded. Though a Republican, Flood represented President Bill Clinton during his 1998 impeachment proceedings, the Post reported .
Approximately 100 activists made their way from the concourse at Manchester Piccadilly onto the tracks at around 1pm.
"We will continue to maintain a police presence at this station and at other stations across the rail network".
"Officers dealt with a number of protesters at #KingsCross with help from @metpoliceUK protestors were prevented from accessing the tracks", a British Transport Police statement said.
Twitter user Lauryn wrote: "There's police surrounding Kings Cross station, I don't wanna get on my train".
Another operator Virgin Trains said the "station remains closed due to protesters".