Passengers leaving or returning to South Yorkshire via Manchester are experiencing extensive delays this afternoon, after protesters climbed onto the train tracks and blocked all rail lines through the station.
National Rail said just after 6.30pm: "Police have successfully dealt with the incident outside the station at London Kings Cross and the station has now been reopened".
Police were called shortly after 1pm and all trains through the station stopped, with knock-on effects nationwide.
It wrote on Twitter: "Manchester Piccadilly has been been closed until further notice".
Virgin Trains said services running to and from the station may be cancelled, delayed or terminated until further notice.
King's Cross in London has been closed today because of a pro-Kurdish demonstration at the station.
"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".
Train services have been ground to a halt by protesters at one of the country's busiest terminals.
They said a normal service was expected to resume after about 3pm.