A knife-wielding woman injured a police officer in Prenton before escaping and going on the run.
Residents in Osborne Road, where the incident occurred, described officers showing members of the public a piece of paper containing an image of a woman.
Merseyside Police made efforts to detain the woman but she managed to escape, causing injuries to an officer in the process.
Residents described seeing a heavy police presence in the area earlier this afternoon.
A statement from Merseyside Police said: "We can confirm that armed police are in Prenton following an incident this afternoon, Monday 30 September.
"At 1.20pm, officers were called to Osborne Road to reports of a woman in possession of a knife.
"An officer sustained minor injuries (not requiring hospital treatment) in attempts to detain her.
"A search is ongoing for the woman at this time and anyone with information is asked to call 999 immediately."
