The demonstrators, who carried signs that read “Stop Turkey from helping ISIS (Daesh) terrorists,” blocked the rail tracks at around 1pm GMT on Sunday, preventing trains from entering or leaving the station.
It was reopened at about 4pm and a normal service is not expected to resume until 6.30pm, according to Network Rail.
British National Rail said in a statement earlier in the day: “The station will remain closed until all protesters have been removed. All trains will remain at the station until it opens. Trains on routes using the station will be terminated short of their destination.”
Images on social media showed protesters sitting on train tracks with yellow banners in support of the YPG (People's Protection Units), a Kurdish militia group.
And just hours later, Kings Cross station, in London, was also closed due to protests.
At around 6pm, National Rail confirmed it was receiving reports police were dealing with an incident outside the London station.
The protests have resulted in services being halted, affecting customers across the country.
Train operators said customers could use their tickets “on reasonable routes” with other companies.
Superintendent Mark Cleland, of British Transport Police (BTP) said: "While we appreciate and respect the right to peaceful protest, when this compromises the safety of the public and the protesters themselves, any offenders will attract the full investigative resources of BTP.
About a hundred protesters believed to belong to the Kuridsh community blocked the railway on Sunday in response to the Turkish government's military offensive against the Syrian Kurdish People's Protection Units or YPG two months ago to clear them from Afrin in north-western Syria.
Similar events are taking place across Europe. At a protest against the Turkish offensive held at the airport in Dusseldorf, brawls broke out between Kurdish and Turkish demonstrators.