Three people - including a police officer - have been stabbed by a man wielding a knife at Manchester Victoria railway station, the BBC reported on Tuesday.
A man and woman in their 50s were attacked at about 20:50 GMT, Greater Manchester Police said.
A British Transport Police officer was stabbed in the shoulder. A man has been held on suspicion of attempted murder.
Officers said counter terrorism police were leading the inquiry, but they were keeping an open mind on the motive.
The station is currently shut and officers remain at the scene.
Greater Manchester Police, which declared the attack a "critical incident", said there was "no intelligence to suggest that there is any wider threat at this time".
Officers said the attack victims' injuries were "serious" but not life-threatening.