An unarmed police officer confronted a man wielding a samurai sword who launched an unprovoked attack on a young Italian woman on a north London street, Scotland Yard said on Monday.

The sergeant, based in Islington, went to the scene of the assault in Holloway Road to find the woman bleeding heavily on the ground and a 25-year-old man brandishing the sword.

Scotland Yard said the attacker, who was challenged to put down the weapon, made several attempts to injure the officer while chasing him, according to the Metropolitan police's account of the incident, which occurred after midnight on Sunday.

The officer then turned, placing himself inside the samurai sword's arc, and forced him to the ground before arresting him. The man is now in custody. A large bag containing a crossbow, more samurai-type swords and numerous hunting knives and gas masks was seized from the suspect.

The 22-year-old woman suffered a number of wounds to the legs, arms and face and was in a serious but not life-threatening condition in hospital, said police. Officers met the woman's parents when they arrived in the UK from Italy and rushed them to the hospital to be with their daughter.

Detective Superintendent Steve Wallace said: "This was a vicious unprovoked stranger attack on a defenceless woman and if it had not been for the officer's bravery and quick thinking the woman and other members of the public could have been killed.

"It takes a very brave officer to tackle a man who you know wants to inflict serious injuries to you with a samurai sword.

"Courage such as this is above and beyond the call of duty and I can't commend the officer highly enough", said Wallace. "The fact that the officer was unarmed and alone when he tackled the man only underlines his bravery.

"He recognised the threat posed by this man and, in a conscious act, positioned himself between the suspect and the public to prevent anyone else being seriously injured."

Wallace said: "Thankfully, this type of incident is rare in London but the public should be reassured that our officers are willing to put themselves in danger to protect the public."