Police, reportedly armed with guns, remain on the street in Toxteth, Liverpool. They were called at around 8.55am after reports two dogs were fighting, and the woman suffered bite wounds to her arm.
Her condition is not life-threatening, Liverpool Echo reports, but she was dashed in an ambulance to hospital.
Witnesses say residents rushed out onto the street after seeing the dog attack a smaller one, possibly a puppy, in the ugly incident.
Lee Grimsditch, a reporter at the scene, tweeted: “Speaking to neighbours it appears the incident involved at least two dogs belonging to a household on the street. Reports one dog, belonging to the same household, attacking another or its puppies.”
A further tweet read: “Neighbours said a large amount of people came outside into the street as the incident reportedly involving dogs took place.”
One resident said: “Police blocked bottom of Lodge Lane, all got guns.”
Another said: “On my way to work this morning looks like a major police incident in Cedar Grove off Lodge Lane in Toxteth.”
Photos show several police cars in attendance.
A spokesman for Merseyside Police said: “We can confirm patrols are currently attending to an incident in Toxteth this morning, Tuesday, 25 May.
“At around 8.55am, officers were called to an address in Cedar Grove after it was reported that two dogs were fighting and a woman had sustained a bite wound to her arm.
“Emergency services are in attendance and the woman’s injury, described as non-life threatening, will be assessed.”
Road closures remain in place while officers deal with the incident and members of the public are advised to avoid the area.
A North West Ambulance spokesman said: “We went to an incident on Cedar Grove, Toxteth, at 09.08 this morning.
“An ambulance took a female patient to hospital.”
More to follow.