A teenage moped rider has been arrested on suspicion of attempting to murder a policeman in north London.

Scotland Yard said the uniformed officer was injured when he was hit by a moped being driven "erratically" in Balls Pond Road in Islington at around 4.15pm on Wednesday.

The 22-year-old policeman signalled for the rider to stop but was ignored before the crash took place.

He suffered leg injuries and was taken to hospital but has since been discharged.

The teenage rider came off his moped and was detained by another officer at the scene.

The 18-year-old man was arrested on suspicion of attempted murder, taking and driving away and possession of a class B drug.

He remains in custody at a north London police station.

Later enquiries found the moped had been reported lost or stolen.

The road was taped off near the junction with Southgate Road as a sea of police vehicles descended on the scene.

Stunned witnesses told how they saw a police officer attempt to stop the rider before he was attacked in broad daylight.

Eyewitness Peter Nguyen, who manages local restaurant Salvation in Noodles, told the Standard: "We were preparing for Chinese New Year when we saw a policeman try to stop a guy on a bike.

"The guy on the moped then smacked the police officer and tried to drive off.

"He got about 15 to 20 feet down the road before the police car stopped him again and pulled him over.

"It was quite scary people were coming out of their houses and shops and staring. The police blocked the road.”

Another witness said: "I saw lots of police officers, more than I've seen before.

"They were gathered by the junction at the end of the road. There was a police van where they were loading a cuffed man into

"As I moved up the road a first response car arrived, followed by a trauma unit."

Witnesses told on social media how swarms of police raced to the scene.

One user Helen Farndon, tweeted: "Absolutely chaos around Balls Pond Road. All roads closed and police everywhere."

Detective Sergeant Jean-Pascal Barbe of Islington Police said: "This shows the dangers that officers face on a daily basis as they go about their work of keeping the people of London safe."

Anyone with information that could assist the investigation is asked to call Islington Police via 101 or @MetCC. Alternatively, contact Crimestoppers on 0800 555 111